Glaser vs WUFI: Comparative Hygrothermal Analysis of Interior Insulation on Solid Brick Walls in Two Climates

ideadmin on 9 February 2026

Glaser vs. WUFI: ¿Qué método es fiable para analizar patologías por humedad en muros macizos con aislamiento interior?

We know that a deep energy retrofits can be delicate, so the question often arises: what tools can I use for the hygrothermal analysis of potential moisture damage?

Glaser vs WUFI: Comparative Hygrothermal Analysis of Interior Insulation on Solid Brick Walls in Two Climates

We know that a deep energy retrofits can be delicate, so the question often arises: what tools can I use for the hygrothermal analysis of potential moisture damage?

In this article, we present a comparison between the simplified Glaser calculation method, as specified in ISO 13788 [1], and dynamic hygrothermal simulation with WUFI Pro 1D [2], in accordance with EN 15026 [3], in two Spanish climates: Barcelona and Burgos. The case study looks at a historic solid brick wall, unrendered, with interior insulation, where we analyse the relative humidity on the interior face of the existing wall, and compare the results from each calculation method. Although ISO 13788 makes clear what the limitations of the Glaser method are, and that it should not be used in cases like this, in practice it is still widely used among building professionals. The results underline the limitations of the simplified method for analysing moisture transport in solid walls with interior insulation.

Introduction

A whole‑building deep energy retrofit radically changes the hygrothermal response of the building envelope. What if I can only install interior insulation on a solid brick wall, exposed to driving rain? Will there be condensation and moisture problems? What tools can I use to analyse the risk? One of the most common tools is the Glaser method, included in ISO 13788. But how reliable are its results?
Let’s look at the results of a comparative study between the Glaser method and a dynamic hygrothermal simulation with WUFI Pro 1D, for a solid brick wall with interior insulation, in the climates of Burgos and Barcelona, Spain.

Figura 1: Cálculo WUFI (izq.) vs. Glaser (der.) — **Figure 1:** WUFI (left) vs. Glaser (right).

What tools can I use for a hygrothermal risk analysis of moisture damage in retrofit projects?

The best‑known calculation method is Glaser, covered by ISO 13788 and developed in 1958 for analysing lightweight assemblies. It is a simplified calculation method, based on monthly average indoor and outdoor temperatures and relative humidity. It assumes:

Steady‑state heat transfer
Moisture transfer only by vapor diffusion
Materials are completely dry at the start

The calculation determines whether there are critical points of condensation over one year, neglecting the following physical processes:

Variation of hygrothermal properties of materials due to their moisture content
Latent heat absorption and release
Capillary suction and liquid transport within materials
Airflow through the building element
The hygroscopic capacity of materials

ISO 13788 states that the method is valid only for building elements where these effects are negligible. So it shouldn’t be used to analyse massive assemblies with interior or exterior insulation, or for elements exposed to rain or subject to freeze–thaw cycles. Spain’s CTE DB‑HE building regulations also explicitly states this premise. Nevertheless, the Glaser method is often used incorrectly in practice.

By contrast, dynamic hygrothermal calculation via numerical simulation—described in EN 15026 and implemented in tools like WUFI and Delphin—addresses Glaser’s limitations through an hourly numerical analysis that considers all the above physical processes, realistic boundary conditions, and initial moisture conditions in materials, reflecting real‑world scenarios in retrofit or new construction.

Comparison: Glaser vs. WUFI — Solid Brick Wall with Interior Insulation

Below are the results of a comparative study between Glaser and WUFI, for the climates of Barcelona and Burgos. A 5‑cm interior thermal insulation layer is applied. A second variant with a vapor barrier on the warm side of the insulation is also studied.

The brick wall is 29 cm thick. Of the 29 cm, 80% is brick and 20% is lime mortar. The one‑dimensional section is subdivided to reflect this brick‑mortar ratio, according to the data in Figure 2, following the methodology of Little et al. [4]. Simulations in WUFI were initialized with materials at a moisture content corresponding to 80% RH, at 20°C. Simulations were run for 10 years, starting in October. The WUFI results presented in the comparison with Glaser correspond to year 10. The wall orientation in the WUFI calculations is north, with a rainwater penetration coefficient of 70%. Basic hygrothermal properties of the sample materials are shown in Figure 2.

Figure 2: Basic hygrothermal properties of materials — **Figure 2:** Basic hygrothermal properties of materials

To compare WUFI results with the monthly Glaser method (whose results do not have an hourly resolution), monthly average values of temperature and relative humidity were extracted from the hourly WUFI outputs.

Results

Figure 3 shows the results for the Barcelona climate with 5 cm of interior insulation. In January, Glaser yields temperatures 16% higher than the dynamic calculation and relative humidity 14% lower.

Figure 4 shows the results for the Burgos climate. In January, Glaser yields temperatures 22% higher than the dynamic WUFI calculation and relative humidity 4% lower.

Figure 4: Results for Burgos, wall with 5 cm interior insulation — **Figure 4:** Results for Burgos, wall with 5 cm interior insulation

Figure 5 shows the results for Barcelona with a vapor barrier installed between the interior insulation and the gypsum plasterboard. In January, Glaser yields temperatures 16% higher than the dynamic WUFI calculation and relative humidity 81% lower. The Glaser method indicates no risk of moisture damage, with a maximum RH of 67%, whereas WUFI indicates a mean RH of 99%, implying risk of moisture‑related pathologies.

Figure 5: Results for Barcelona, wall with vapor barrier + 5 cm interior insulation — **Figure 5:** Results for Barcelona, wall with vapor barrier + 5 cm interior insulation

Figure 6 shows the results for the Burgos climate. The trend is identical: the Glaser results yield much lower relative humidity values than the dynamic calculation with WUFI.

Figure 6: Results for Burgos, wall with vapor barrier + 5 cm interior insulation — **Figure 6:** Results for Burgos, wall with vapor barrier + 5 cm interior insulation

Conclusions

In Barcelona without a vapor barrier, the relative humidity results on the interior face of the existing wall are 2% to 28% lower with the Glaser method than the dynamic WUFI results. In Burgos, the difference ranges between 2% higher and 26% lower.

For the wall with a vapor barrier, the difference is much more pronounced: from 48% to 81% lower in Barcelona, and from 62% to 116% in Burgos.

The results indicate that the Glaser method described in UNE‑ISO 13788 is not suitable for analysing moisture transfer in unrendered solid walls exposed to rain with interior insulation. The large discrepancy between the results may lead to incorrect hygrothermal design and potential interstitial moisture damage.

For situations like this, that are hygrothermally sensitive, we recommend carrying out a dynamic calculation and/or consulting a specialist. We also recommend extending the study to analyse the water content of materials and the effect of air infiltration/exfiltration (beyond an analysis of relative humidity on the interior face of the wall). In addition, we recommend in‑situ testing to determine the liquid transport coefficient of a historic solid brick wall, since its hygrothermal behaviour can vary widely.

References

[1] EN ISO 13788:2016. Hygrothermal performance of building components and building elements — Internal surface temperature to avoid critical surface humidity and interstitial condensation — Calculation methods (ISO 13788:2012).

[2] WUFI (Wärme Und Feuchte Instationär): dynamic hygrothermal simulation software for analysing heat and moisture transport in building components, developed by the Fraunhofer Institute, Germany.

[3] EN 15026:2007. Hygrothermal performance of building components and building elements — Assessment of moisture transfer by numerical simulation.

[4] Joseph Little, Carolina Ferraro & Beñat Arregi (2015). Assessing risks in insulation retrofits using hygrothermal software tools. Heat and moisture transport in internally insulated stone walls. Historic Environment Scotland Technical Paper 15, Second Edition, 2015, Edinburgh, Scotland.

[5] ASHRAE 160‑2016. Standard 160‑2016 — Criteria for Moisture‑Control Design Analysis in Buildings (ANSI Approved).

Passivhaus EnerPHit certification for existing buildings: What is it and how to achieve it?

ideadmin on 8 January 2026

EnerPHit: certificación Passivhaus para rehabilitación de edificios existentes. ¿Qué es y cómo conseguirla?

As the demand for energy-efficient buildings continues to grow, the retrofit of existing buildings to meet modern efficiency standards has become increasingly important.

Passivhaus EnerPHit certification for existing buildings: What is it and how to achieve it?

As the demand for energy-efficient buildings continues to grow, the retrofit of existing buildings to meet modern efficiency standards has become increasingly important.

Passivhaus EnerPHit certification provides a rigorous and effective framework for deep energy retrofits, ensuring optimal energy performance and comfort. This article outlines the pathways to achieving EnerPHit certification, its advantages, and considerations for partial renovations.

Pathways for achieving EnerPHit certification

There are two primary pathways to achieving EnerPHit certification: performance-based and prescriptive, together with common requirements that apply to both. Let’s take a look at each one.

1. EnerPHit Energy Demand Method

This performance-based approach is similar to Passivhaus certification for new builds but with slightly relaxed heating and cooling demand requirements, adjusted for the seven global climate zones defined by the Passivhaus Institute, shown in Figure 2.

Figura 2: Criterios de demanda energética EnerPHit (Fuente: Passivhaus Institute, Criterios para edificios, Versión 10c del 20/09/2024) — **Figura 2: Criterios de demanda energética EnerPHit** (Fuente: Passivhaus Institute, Criterios para edificios, Versión 10c del 20/09/2024)

Figura 3: Rehabilitación EnerPHit por Demandas, Girona, LPR Arquitectes — **Figure 3: Multi-residential building certified to EnerPHit standard, Energy Demand Method, Girona, Catalonia, RPR Arquitectes**

2. EnerPHit Building Component Method

This prescriptive approach sets maximum thermal transmittance values (“U-values”) for each building element, requires control of solar gains, and establishes minimum performance requirements for mechanical ventilation with heat or moisture recovery, depending on the climate zone (Figure 4). The aim is to ensure that the retrofit is highly energy-efficient and safe with respect to moisture-related pathologies.

Figure 4: EnerPHit Building Component Method (Source: Passivhaus Institute, Criteria for Buildings, Version 10c as of 1/20/2023) — **Figure 4: EnerPHit Building Component Method** (Source: Passivhaus Institute, Criteria for Buildings, Version 10c as of 1/20/2023)

Figura 5: Rehabilitación EnerPHit por Componentes, Sant Cugat del Vallès, Marcove (Fuente: Jose Hevia) — **Figure 5: Single-family home certified to EnerPHit standard, Component Method, Marcove, Sant Cugat, Catalonia** (Source: Jose Hevia)

Common requirements (for both pathways)

For both pathways, there are common requirements. Regarding the level of air infiltration, the maximum allowed value in the airtightness (Blower Door) test is n50 = 1.0 air changes per hour (instead of n50 = 0.6 ach required by Passivhaus for new builds). Additionally, the total renewable primary energy consumption of the building is limited, depending on whether it is certified as EnerPHit Classic, Plus, or Premium (Plus and Premium include renewable energy generation), as shown in Figure 6. Each certification class has its respective seal, shown in Figure 7.

Figure 6: General EnerPHit criteria (irrespective of the method) (Source: Passivhaus Institute, Criteria for Buildings, Version 10c as of 1/20/2023) — **Figure 6: General EnerPHit criteria (irrespective of the method)** (Source: Passivhaus Institute, Criteria for Buildings, Version 10c as of 1/20/2023)

Figure 7: EnerPHit Classic, Plus y Premium seals

Advantages of EnerPHit certification

Pursuing EnerPHit certification provides numerous benefits:

Holistic deep energy retrofit: Ensures comprehensive upgrades that prevent moisture damage associated with partial retrofits.
Up to 90% energy savings: Significant reductions in space heating and cooling costs.
Enhanced indoor air quality: Mechanical ventilation with heat recovery (MVHR) ensures a controlled, fresh, and comfortable air supply.
Superior thermal comfort: High-performance insulation and airtightness eliminate cold spots and drafts.
Efficient HVAC systems: Optimized heating, cooling, and hot water systems reduce energy consumption.
Lower life-cycle carbon emissions: Avoids “lock-in” effects where partial renovations leave high CO2 emissions unaddressed for years.

Figura 8: Can Mati, Viladecans, rehabilitación EnerPHit por Componentes, Daniel Tigges Architekt (Fuente: Pol Viladoms) — **Figure 8: Can Máti, Viladecans, townhouse EnerPHit retrofit, Component Method, Daniel Tigges Architekt** (Source: Pol Viladoms)

Step-by-step retrofits and partial renovations

For phased retrofits, buildings can receive pre-certification for all steps up to the final complete retrofit, under an EnerPHit Retrofit Plan (ERP). This ensures that when all phases are complete, the building meets EnerPHit standard. Pre-certification offers reassurance to owners and planners that performance targets will be achieved and helps spread the investment over a longer period.

EnerPHit Unit certification is also available for individual apartments within multi-residential buildings. This requires:

Airtightness verification: Either a pressure test (qe 50 ≤ 1.0 m³/(hm²)) or detailed documentation and photographic evidence of airtight construction.
Connection to adjacent spaces: Measures to ensure the retrofit works don’t generate moisture damage in neighbouring units.

Conclusions

EnerPHit offers several pathways to achieve Passivhaus certification. When carrying out an energy retrofit, it’s especially important to implement improvements in a way that avoids moisture damage. EnerPHit certification provides reliable and safe methodologies to avoid this, ensuring that existing buildings meet modern standards of efficiency and comfort, while significantly reducing their environmental impact.

Which Christmas tree is greener? Real, artificial, or potted?

ideadmin on 19 December 2025

A real tree which we then take to the recycling centre? A real tree, but potted, which we could then re-use every year. Or a plastic tree which we could re-use for several years.

Which Christmas tree is greener? Real, artificial, or potted?

We’re having family to stay in our new house for Christmas, and so I got talking to my daughter a few days ago about what we were going to do for a Christmas tree. Some years ago, we made a Christmas tree mobile, with sticks and leaves, which we decorate with LED lights and a choice selection of festive tinsel and Christmas ornaments. But what about pushing the boat out this year?

We ended up having an interesting, and fully woke discussion, about what would be the most environmentally friendly solution:

A real tree which we then take to the recycling centre?
A real tree, but potted, which we could then re-use every year (if we could keep it alive…).
Or a plastic tree (which we weren’t very keen on, but…) which we could re-use for several years.

So which option has the lowest carbon footprint? Here’s what the data says:

Artificial Tree: Manufacturing a 2 m PVC tree emits about 40 kg CO₂e. If you reuse it for 10+ years, its annual impact drops to ~4 kg/year, making it competitive (that is: 40 kg CO₂e spread over 10 years of use, means the average yearly emissions are 4 kg CO₂e/a …).

Real Tree (which is then composted): this option generates round 5 kg CO₂e per year. Composting or chipping is key to keep emissions low.

Real Tree (Landfilled): this is the worst option—up to 16 kg CO₂e per year due to the methane emissions from the rotting biomass (methane was a Global Warming Potential about 27 times higher than CO₂).

Real Tree (Burned/Incinerated): this generated about 3.5 kg CO₂e per year, which is better than landfill, especially if it’s burnt in energy recovery facilities, where the heat is used for some other purpose.

Potted/Replantable Tree: This one is the winner in the long-term—roughly 20 kg CO₂e over 10 years if cared for and reused annually.

Bottom line:

If you already own an artificial tree: keep using it as long as possible.

If you want a real tree: choose local, and compost or incinerate responsibly.

If you want the greenest choice, go for a potted tree which you can reuse or replant.

Sources:

Carbon Trust – Life Cycle Assessment of Christmas Trees
Zurich Insurance – Sustainability tips for festive season
ADEME (Agence de la Transition Écologique) – Environmental impact of natural vs artificial trees

First summer in our Passivhaus: comfort, coolness and energy savings

ideadmin on 12 November 2025

First summer in our Passivhaus: comfort, coolness and energy savings

By Oliver Style, Praxis CEO

I’ve worked on Passivhaus projects for more than a decade now, based here in Catalonia, north-east Spain. I came across the standard when I was doing a Masters in Architecture, Energy and Environmental studies at Centre for Alternative Technology in Wales (UK). Passivhaus resonated with me…it made sense: to design, build, and retrofit buildings that are super comfortable, need very little energy and radically reduce CO2 emissions. So choosing a passive house was a way of living more coherently, and a personal statement of intent to fight against the climate emergency…of living better, with less.

It wasn’t until last year that I was able to take part in the design and construction of my own Passivhaus, Can Naiades, a prefabricated lightweight timber frame house located about 40 kilometres northeast of Barcelona, with a useful floor area of 128m². Having heard from many clients about how wonderful it is to live in a Passivhaus, it’s quite different to experience it first-hand. What does it feel like? It feels solid, comfortable, and quiet. It feels safe, airy and light. It is everything I’ve never had in any of the houses I’ve previously lived in and complained about. It really is, GREAT!

Surfing the heat waves

We moved in at the end of May 2025 and walked slap bang into the middle of a major heat wave, with average temperatures around 4 ºC higher than previous years and peaks of 37 ºC. Walking outside was like stepping into a furnace. We had no blinds for all of June and July (they were only installed in August), but despite that, it was wonderfully cool and comfortable. We did- of course- have our (one) air conditioning unit on quite a lot…but even so, our energy use from June-October was 3 % lower than predicted with the (calibrated) PHPP energy model. Fantastic!

The house has really worked a treat this first summer. Plenty of people complain that lots of insulation and airtightness means passive houses overheat in the summer. But, despite large amounts of glazing, Can Naiades has kept us nice and cool all summer, with 96% of our energy use coming directly from the solar PV panels and battery bank.

Temperature-wise, there is a noticeable difference between the ground floor (which has a big fat concrete floor slab with lots of thermal inertia), and the 1^st floor (which has very little thermal mass). Heat rises of course, so to some degree that’s as expected…but a bit of thermal inertia really does help shave the peaks of those daily temperature swings.

Powered by the sun

Between June and October, we used only 137 kWh from the grid. We got our grid feed-in connection legalised at the end of September, so in October, 57% of the energy we generated with the PV panels we used in the house and pumped the remaining 43% into the grid…clean, fossil-fuel-free electricity.

And then we got our 1^st energy bill: 19 € for the month of August, of which only 3€ was for the electricity we consumed from the grid (in total 18 kWh, or 0.15 €/m²). In the 80m²flat we used to live in, we used 475 kWh the previous August and paid 95 € for a month of electricity (1.19 €/m²)…that’s 87% less (in €/m²). Bargain!

It’s a wrap!

I remember a friend telling me once, that the only problem with living in a Passivhaus is that you don’t sleep very well when you go and stay anywhere else! There are still a lot of jobs to finish in the house and we’re skint, so we’re not going very far for the foreseeable future…but I can confirm: living in a Passivhaus is a dream come true, especially in a Mediterranean summer!

But it shouldn’t be a luxury: it should be normal, and within everyone’s reach. In the context of a serious housing crisis in many European countries, decent, comfortable, and efficient homes should be accessible to the majority of the population- especially for low-income families, who often live in a situation of energy poverty. Both the public and private sector need to work to make this a reality.

For more tecnical information about the project, have a look at this article.

Can Naiades: professionals & contractors

Architect: Daniel Tigges – Tigges Architekt
Quantity Surveyor/Site Supervisor/H&S: Josep Maria Fosalba – Oftecnics
Passivhaus design, MEP system design & Blower Door testing: Praxis Resilient Buildings
Final Blower Door test: Timo Hoek – Air Test
Passivhaus Certification: Micheel Wassouf – Energiehaus Arquitectos
Health & geobiological analysis: Sonia Hernandez – Arquitectura Sana
Contractor: House Habitat
MEP installation: Fontalgar Instalaciones
Monitoring & control system installation: John Kregel – Hebhaus
Solar PV installation: Prot Energia
Shading devices: Griesser España & Buohome
Ventilation: Zehnder

Can Naiades: components and systems

Insulation: Panel Plus TP138, Smart Wall FKD-N Thermal, Knauf Insulation
Specialist insulation: Nanoboard Aerogel, Pafile
Timber structure: EGOIN
Windows: Smartwin Compact, Ventanas Gardea
Window subframes: ISO-TOP construction sheets WF3, Iso Chemie
Airtightness tapes & membranes: SIGA & Onhaus
Liquid airtight membrane and radon gas barrier: Soudatight SP & LQ, Soudal
Radon gas sensors: Bequerel
Control & monitoring system: Loxone
Rainwater catchment tank: Simop 6328
Grey water treatment system: Intewa Aqualoop, Ecospai
Shading devices: Solomatic II 80 FIX, Griesser España
Rooflight: DEC-C U8 + AMZ/C Z-Wave awning blind, Fakro
Heat pump (heating, cooling, hot water): Aquarea Ecoflex, Panasonic
DHW heat recovery systems: Zypho iZi 30 & Zypho PiPe 65, Aliaxis
MVHR unit: Zehnder ComfoAir Q450 ERV + ComfoClime Q, Zehnder
Solar PV system: 21 TwinPeak5 410W PV panels; 1 Primo GEN24 8.0 Plus hybrid inverter; BYD B-Box Premium HVM 13.8kW battery bank, Prot Energia

Tigges Architekt

Aliaxis

Arquitectura Sana

Bequerel

Ecospai

EGOIN

Energiehaus Arquitectos

Fontalgar Instalaciones

FAKRO

Ventanas Gardea

Griesser

HEBHAUS

House Habitat

Iso Chemie

Knauf Insulation

Loxone

Pafile

Panasonic

Petwalk

Prot Energia

SIGA

Soudal

Zehnder

Masies de Mollet & Mirador de Gracia achieve n50=0.6 ACH in their Final Blower Door Tests!

ideadmin on 10 September 2024

¡Las residencias Masies de Mollet & Mirador de Gracia logran n50=0,6 ren/h en sus ensayos finales de Blower Door!

Two recently completed care homes in Barcelona, now in the final stages of Passivhaus Certification, have reached an outstanding n50=0.6 ACH in their final Blower Door tests.

Masies de Mollet & Mirador de Gracia achieve n50=0.6 ACH in their Final Blower Door Tests!

Two recently completed care homes in Barcelona, now in the final stages of Passivhaus Certification, have reached an outstanding n50=0.6 ACH in their final Blower Door tests.

This remarkable achievement makes them the largest and most airtight buildings ever constructed in Catalonia!

Residencia Mirador de Gracia

Developed by FIATC Residencies and designed by Joaquim Rigau of GENARS, with Passivhaus design from Praxis

The two care homes Masies de Mollet and Mirador de Gracia are on the home straight for achieving Passivhaus Classic certification.

Thanks to a high-performance thermal envelope and highly efficient ventilation, heating, cooling and hot water systems, they will offer exceptional indoor air quality, superior thermal comfort, and projected savings of 70% in operational running costs compared to the owner’s other care homes.

Blower Door test

A Blower Door test is used to assess a building’s air
permeability, helping to locate and seal air leaks and drafts.

Achieving a high level of airtightness is essential for Passivhaus buildings. The principle of “build tight, ventilate right!” helps reduce heat loss by up to 30%, while improving thermal and acoustic comfort, and maximizing the efficiency of mechanical ventilation, heating, and cooling systems.

Mirador de Gracia

Floor area [m²]	4595
Internal Volume [m³]	13863
Building height [m]	29
Infiltration rate @50 Pa q₅₀ [m³/h]:	8912
Infiltration air charge rate @50 Pa n₅₀	0.6

Masies de Mollet

Floor area [m²]	4566
Internal Volume [m³]	15624
Building height [m]	15
Infiltration rate @50 Pa q₅₀ [m³/h]:	9758
Infiltration air charge rate @50 Pa n₅₀	0.6

In both the Mirador de Gracia and Mollet projects, Praxis played a key role in preparing the construction teams.

They delivered online Site Supervisor training to the design and construction teams before breaking ground. The courses covered the essential requirements for Passivhaus certification, including airtightness strategies, insulation specifications, thermal bridge-free detailing, and HVAC and DHW commissioning.

On-site, Praxis conducted Passivhaus supervision and carried out preliminary Blower Door tests. Given the complexity of the buildings, the Mirador project required 10 preliminary tests—both partial and full—to identify leaks and seal them. The Mollet project underwent 6 preliminary tests before successfully passing the final assessment. Airtightness was achieved using gypsum plaster on exterior walls, reinforced concrete slabs for the ground floors and roofs, and windows sealed with tapes to the airtight layer, using Ampacoll Fenax tapes supplied by Ecospai. Service penetrations were sealed using flexible foam and airtight paint. A 1:1 full-scale mock-up was also built and tested, providing the construction teams valuable hands-on experience.

After overcoming numerous challenges and a fair number of sleepless nights, the Praxis team, led by Oliver Style, celebrates this significant milestone in Passivhaus construction in Spain. Work continues on four more Passivhaus care homes for the same developer, all aiming for certification. Stay tuned!

Residencia Masies de Mollet

Delivering large Passivhaus buildings: Site Supervisor & Construction Verifier training

praxisadmin on 12 July 2024

Our experience with Site Supervisor and Construction Verifier training is that the courses provide architects and engineers with the tools they need for successful site supervision and navigation of the certification process, and deliver important on-site savings for developers and contractors.

Delivering large Passivhaus buildings: Site Supervisor & Construction Verifier training

The article presents the experiences and lessons learned from our Passivhaus Site Supervisor and Construction Verifier training courses.

The courses provide architects and engineers with the tools they need for delivering large and complex Passivhaus buildings, achieving certification and reigning in cost overruns.

Delivering large Passivhaus buildings — Photo: © Joan Giribet

Large and complex Passivhaus buildings: reducing risk and reigning in cost overruns through practical online training

“Your course has saved me at least 20,000 € in construction costs”

This was the feedback we got from the developer of a small multi-residential building we consulted on, following the online Site Supervisor course we gave to his team. The building was developed, designed, and built by a team with no prior experience in Passivhaus and has now achieved Passivhaus Classic certification.

Lack of experience increases the risk of cost overruns during the construction phase- particularly in relation to the execution of the airtight layer and achieving the required result in the final Blower Door test. Our experience with Site Supervisor and Construction Verifier training is that the courses provide architects and engineers with the tools they need for successful site supervision and navigation of the certification process, and deliver important on-site savings for developers and contractors.

Using a Barcelona street advertising format to publicise the Site Supervisor course

Using a Barcelona street advertising format to publicise the Construction Verifier course

Another client, FIATC Residencias, who are developing 7 elderly people’s residencies that are all aiming for Passivhaus certification, have made our Site Supervisor and Construction Verifier course obligatory for the contractors, installers, and design teams on each project, with 3 courses held to date. In the course satisfaction survey, one student reported:

“I particularly want to highlight how useful it was to get all of us who’ll be working on-site together on the course, including both civil works and mechanical and electrical contractors”.

Bridging the gap between Passivhaus design and Passivhaus construction: online Site Supervisor & Construction Verifier training

According to the PHI database, as of 2023, there were over 700 certified Passivhaus Designers in Spain and over 1300 Passivhaus Tradesperson, compared with 195 and 25 respectively in Germany. This suggests that Passivhaus design and tradesperson training has got off to a good start in the construction sector.

However, despite extensive Passivhaus Designer and Tradesperson training, there is a clear knowledge gap when it comes to the construction and certification of large and complex Passivhaus buildings. This is where the official Passivhaus Site Supervisor and Construction Verifier courses come in: they are especially designed to fill that gap, helping contractors, installers, site managers and tradespeople in the successful execution of large and complex Passivhaus buildings, on time, on budget, and compliant with Passivhaus certification.

While the courses can be taken by any construction professional, those with Tradesperson and Designer qualifications can acquire the Site Supervisor or Construction Verifier add-ons, if they take the course and pass the exam (shown in Figure 2). At the time of writing, we have held two exams, leading to the first qualified Site Supervisors and Construction Verifiers in Spain.

The format used for the courses and for the exam is 100 % online, making an easier fit with on-site work and other commitments. Exam preparation includes an intensive on-line class, with review of the course content and question and answer time. The Site Supervisor exam must be completed in under 45 minutes, and the Construction Verifier exam in under 2 hours, both done online.

Praxis uses proprietary course material, based on abundant practical examples of on-site situations using photographs and videos. During each course, there are always two trainers, one giving the content and another attending the live chat, launching surveys, and posting references to documentation on the online campus, where 77 technical articles, guides and how-to documents are available for reading and download. A forum in the online campus provides a space for participants to ask questions, exchange ideas, and generate debate. The participants on our courses are often from very different countries and technical backgrounds, providing a rich and diverse learning environment.The Site Supervisor course consists of 4 modules, while the Construction Verifier course includes 8 modules, with the courses held concurrently.

Summary of the modules for each course and their content

Course	Course	Module	Content
Construction Verifier		1	Navigating Passivhaus Certification
Construction Verifier		2	Navigating Passivhaus Certification
Construction Verifier	Site Supervisor	3	Insulation and thermal bridges
Construction Verifier	Site Supervisor	4	Windows, doors and curtain walls
Construction Verifier	Site Supervisor	6	Airtightness
Construction Verifier	Site Supervisor	6	Mechanical & electrical services
Construction Verifier		7	Commissioning
Construction Verifier		8	Monitoring & performance verification

Every online session includes a guest speaker, presenting a specific technical issue relating to the module in question. Both during and at the end of each session, multiple choice questions are presented online to the students, to consolidate learning and generate debate and reflection. Each online session is also recorded and made available for watching offline, with attendees commenting that they found them to be a useful resource for reviewing and taking notes after the online classes. Additionally, and to provide networking opportunities, we offer site visits for all students, so they can see a Passivhaus building under construction in the month or two following the course.

Feedback

Each course includes on online student satisfaction survey. Some of the answers provide by students are shown below:

“I feel very satisfied, it’s everything I expected and more. It has an eminently practical tone, without undermining theoretical concepts. The technical level of the classes has been very high, and the range of speakers presenting real projects has been very instructive. This course is very effective for training design teams in the actual construction process.”
“A very practical course. I found the review of concepts, drawings, and photos very useful to detect good and bad practices. The quality and quantity of information is very positive, the course structure is well organized.”
“I’m very happy to have taken the course. I feel like I learned a lot and that I’ve taken an important step forward as a professional specialised in Passivhaus construction.”

Filling the gap for a successful execution of large and complex Passivhaus buildings

Official Passivhaus Site Supervisor and Construction Verifier courses come in: they are especially designed to fill that gap, helping contractors, installers, site managers and tradespeople in the successful execution of large and complex Passivhaus buildings, on time, on budget, and compliant with Passivhaus certification.

The growth in Passivhaus construction in Spain in recent years has been significant: in 2021, Spain was ranked 2^nd in the world after China, with the most square meters of floor space certified to the Passivhaus standard. Increasingly, larger, and more complex Passivhaus buildings are being designed or retrofitted, tendered and built by large “mainstream” contractors and installers who often have little experience in executing Passivhaus buildings. The Site Supervisor and Construction Verifier courses provide contractors, installers, site managers and tradespeople with the knowledge they need for the successful execution of large and complex Passivhaus buildings.

Praxis at the 27th International Passive House Conference

ideadmin on 6 May 2024

The International Passive House Conference is a benchmark event in the construction sector, where professionals from all over the world meet to analyze the latest trends in Passivhaus and high performance buildings. Held in the alpine city of Innsbruck in Austria, the event combined technical presentations, visits to passivhaus buildings and an exhibition of innovative materials and components for sustainable and energy efficient construction.

Praxis at the 27th International Passive House Conference

Held in Innsbruck, the International Passivhaus Conference combines technical presentations and visits to Passivhaus buildings.

Recent developments were presented, such as the new protocol to certify apartments within multi-family residential buildings.

Praxis at the 27th International Passive House Conference

The International Passive House Conference is a benchmark event in the construction sector, where professionals from all over the world get together to look at the latest trends in Passivhaus and high performance buildings. Held this year in the alpine city of Innsbruck in Austria, the event combined technical presentations, visits to passivhaus buildings and an exhibition of innovative materials and components for sustainable and energy efficient construction.

Recent developments were presented, such as the new protocol to certify apartments within multi-family residential buildings. This means it won’t be necessary to carry out a step-by-step retrofit plan to obtain EnerPHit certification, and will simplify the work for Passivhaus Designers and Certifiers, while offering a solution to owners who want to retrofit and certify their apartment. Also, a new simplified version of the PHPP was presented, for the certification of single-family homes. The idea is to streamline the design and certification process for this type of property.

Praxis CEO Oliver Style gave a presentation on the Site Supervisor and Construction Verifier training courses we provide at Praxis, which have helped developers, contractors and designers minimise risk and cost overruns. He explained how the seven editions of both courses have equipped more than 80 attendees with the tools and knowledge needed to bridge the gap between design and construction for large and complex Passivhaus projects.

It was exciting to be able to meet so many professionals from such a range of countries and share ideas on how to transform architecture and create more efficient, healthy and comfortable buildings. In these two videos, Bega Clavero and Macarena Rossetti, Passivhaus Designers at Praxis, share their experience at the 27th edition of the International Passive House Conference:

Can Naiades: 15 steps towards a comfortable, healthy home, resilient, and efficient home

ideadmin on 13 November 2024

Can Naiades is a single-family, 4 bedroom, 2 storey Passivhaus Plus home, located in Sant Julia d’Alfou, Spain. Designed by Daniel Tigges from Tigges Architekt, and Praxis Resilient Buildings providing Passivhaus design.

Can Naiades: 15 steps towards a comfortable, healthy, resilient, and efficient home

Can Naiades is a single-family, 4 bedroom, 2 storey Passivhaus Plus home, located in Sant Julia d’Alfou, in the province of Barcelona, Catalonia, Spain. Designed by Daniel Tigges from Tigges Architekt, with Oftecnics as Quantity Surveyor/Site Supervisor, the house is built by House Habitat, with Fontalgar Instalaciones installing electrical and mechanical services, and Praxis Resilient Buildings providing Passivhaus design, HVAC system design and Blower Door testing. The house is being certified to Passivhaus standard by Micheel Wassouf of Energiehaus Arquitectos.

1. Bioclimatic design

The house is built on a site that is sloped from east to west, with large stone retaining walls creating a platform where the house can sit with the longest façades aligned south / north. To maximise solar gain and daylighting, the windows on the southern façade make up 72% of the total window area, meaning that around 79% of the home’s heating requirements will be provided by the sun (14% will be provided by internal heat gains and the remaining 7% by the active heating system). Southern glazing is shaded in the summer by the balcony on the intermediate floor and a roof overhang, with external venetian blinds on all windows. The house has a relatively compact design with a heat loss form factor of 462 ÷ 128 = 3.6 (total envelope area ÷ treated floor area).

2. Geobiological survey

Early in the design process, a geobiological survey of the site was done by Architect Sonia Hernandez from the Arquitectura Sana, to measure electromagnetic radiation on the plot and identify possible sources of contamination. Low frequency electric and magnetic fields, high frequency electromagnetic fields, geological alterations, gamma and neutronic radiation, and terrestrial magnetic fields were measured. The results of the survey showed some terrestrial magnetic fields where beds were located in two of the first-floor bedrooms. The layout of the upstairs bedrooms was therefore modified to avoid potential health problems associated with long-term exposure. Another recommendation from the survey was to ensure that cabling in the bedrooms was shielded to avoid electromagnetic radiation while sleeping. As far as possible, low emission materials have been used to reduce indoor contaminants.

3. Timber structure

The house is built with a lightweight timber structure assembled off-site by EGOIN, in the Basque country (northern Spain), using local radiata pine timber. The wall modules consist of 140mm timber studs, filled with recycled glass wool insulation and enclosed internally with a 12mm particle board and externally with a 12mm OSB 3 board.

The roof modules consist of 200mm joists, filled with recycled glass wool insulation, enclosed internally with a dynamic vapour control membrane and externally with an 18mm OSB 3 board.

The intermediate floor and roof modules all came factory fitted with a SIGA Wetguard waterproof membrane, to protect them from rain during on-site assembly. Due the double height design in the sitting room area, a part of the structure on the northern façade consists of 150mm Cross Laminated Timber (CLT) panels, together with a steel frame structure.

The wall and roof modules were delivered to site and the house was erected and waterproofed in only 8 working days, bringing with it all the advantages of off-site prefabrication: rapid onsite assembly, greater precision and build quality, less waste, and optimization of materials.

4. Earthing system

A good earthing system is particularly important in timber houses, to avoid electromagnetic radiation from cables and appliances that can affect occupants’ health. To this end, four 3-meter cooper earth rods were installed, connected to an earth cable, in turn connected to the reinforced steel structure of the concrete floor slab. The reinforced steel structure itself was also welded at specific points to ensure a good electrical connection across the slab. The connections between copper and steel were sealed with a special paste to prevent galvanic corrosion and ensure a good earth connection for the working life of the building. A resistance to ground of ≤ 6 Ohms is recommended: once the earthing system was complete, the measured result was 2.15 Ω. Fantastic!

5. Thermal insulation

The walls and roof of Can Naiades are insulated with Knauf Insulation recycled glass wool insulation, chosen for fire resistance, good thermal performance and because they incorporate a bio-based E-Technology binder, free from added phenols and formaldehydes, protecting both the workers on site and future occupants from harmful emissions. The walls are insulated within the timber structure with 140mm, together with 60mm externally, and a further 50mm in the internal service void. The roof has 200mm of insulation between the timber structure, and a further 150mm on top. Between 100mm and 200mm of XPS insulation has been installed under the concrete floor slab. Supplied by Pafile, small amounts of aerogel- about the most insulating material there is for use in buildings- has been used to insulate specific sections of steel I-beams that were needed to reinforce the structure. Steel is a good heat conductor, so the aerogel blankets reduce thermal bridging, heat loss and cold spots where the steel penetrates the thermal envelope.

6. Radon gas barrier

The floor slab is painted with a Soudatight liquid membrane made by Soudal, to form a radon gas barrier. This prevents the entrance of radon gas, which is naturally occurring, carcinogenic, invisible, and odourless, emitted from granitic rocks, and which can seep into building through floor slabs and walls to ground (for more information, see this article on radon gas).

7. Openings

The windows consist of triple glazed, argon-filled, low emissivity glazing and Passivhaus certified Smartwin timber-aluminium window frames made by Ventanas Gardea. Window thermal bridges are reduced to a minimum by insulating most of the fixed part of the frames. For the sills of the sliding and french windows, the frames are installed on an Isotop Winframer high density EPS board made by Iso Chemie, to reduce thermal bridging and cold spots. A FAKRO DEC quadruple-glazed roof light provides daylighting to the stairwell to the north. A Passivhaus certified airtight and insulated Petwalk cat flap will let the cat in and out with minimal heat loss.

8. Airtightness and vapour control

SIGA airtight tapes have been used for all the airtight sealing. A SIGA Majrex 200 dynamic membrane provides the air barrier and vapour control layer in the roof. The membrane has a variable vapour diffusion resistance, which means in winter it acts as a vapour barrier, and in summer, it lets vapour pass through. This protects the roof modules from the exfiltration of warm and humid air in the winter (important for avoiding interstitial condensation damage in flat non-ventilated timber roofs) and allows back drying in the summer (in case any humidity has accumulated during the winter, or due a water leak- whether during construction or in the future). A FINSA Superpan VapourStop particle board provides the air barrier and vapour control layer in the external walls. The house will undergo a whole-building Blower Door airtightness test, to meet the stringent Passivhaus requirement of n50 ≤ 0.6 ach. This means the equivalent total surface area of all the air leaks in the house will constitute a hole about 10cm x 10cm.

9. Ventilation

Clearly you can’t build an airtight, draught-free home without making sure the space is adequately ventilated, otherwise air quality would be terrible and there’d be way too much humidity in the indoor air. Added to this, every day, while we eat an average of 1kg of food and drink around 2 litres of water, we breath around 8000 litres of air. So reliable ventilation and good air quality are really important! In Can Naiades we’re using a Zehnder balanced whole-house mechanical ventilation system with heat recovery, that recovers around 90% of the heat from outgoing stale air and uses it to preheat incoming air. In the summer the heat recovery process is reversed, whereby incoming air is cooled by the relatively cooler outgoing stale air. If the outdoor air temperature is lower than the indoor temperature, an automatic bypass opens so that relatively cooler outdoor air is let in directly, providing “free cooling”. In the entire process, the heat recovery unit consumes about the same amount of electricity as 2 low-energy light bulbs. The system blows pre-heated (or pre-cooled in the summer) fresh air into the bedrooms, sitting room and office, and extracts stale air from the kitchen and bathrooms, working 24 h/d, 365 days/year, silently and efficiently. The heat recovery unit includes a F7 filter on the incoming outdoor, removing pollutants in the outdoor air, which will mainly come from wood fires in the winter.

10. Keeping cool in the summer

Heat waves have been a feature of recent years, and are set to increase over the coming decades, so a series of design strategies have been implemented that will help keep the house cool, using very little energy. A balcony between the ground and first floor, together with the roof overhang, shade the southern glazing in the summer. All windows have Griesser Solomatic external venetian blinds, with slats that can be adjusted to let in natural light but block direct sunlight. The FAKRO roof light has an external awning to block solar gain, together with a motorised opening mechanism, which means it can be opened when it’s hot inside and cooler outside, drawing cool air in through the ground floor and 1^st floor bedrooms and out through the roof light. The height difference provides higher air flow rates through what’s called the “stack” effect. The office and bedroom windows all have mosquito netting so then can be left tilted open at night, without bugs coming in. As in vernacular Mediterranean architecture, the house is rendered white on most of the façade, which means it reflects more sun in the summer and keeps cooler. 3 deciduous black poplar trees to the south and west of the house have been kept in place, to provide additional shading in the summer.

11. Heating & cooling

Comfort heating and cooling is provided by a Zehnder ComfoClime Q autonomous heat pump heating/cooling coil on the ventilation system. In heating mode, the heat pump extracts heat from the extract air and passes it to the supply air, heating it to up to 49ºC. In cooling mode, the unit extracts heat from the supply air and passes it to the extract air, cooling it down to 12ºC. This way, during most of the year, the heating and cooling needs of the home will be covered by the ventilation supply air, providing up to 3.8 kW of heating power and 1.7 kW of cooling power at a flow rate of 400 m3/h.

For peak cooling loads, a Panasonic Aquarea Ecoflex heat pump with a 7kW indoor ducted split unit, recirculates indoor air and removes heat from the building. Instead of dumping that heat to the outdoor air (as traditional air conditioners do) the Ecoflex recovers heat and transfers it the Domestic Hot Water (DHW) tank, thus reducing summer hot water energy consumption.

12. Domestic Hot Water (DHW)

The Panasonic Aquarea Ecoflex heat pump produces hot water for washing and showering, extracting heat from the outdoor air and transferring it to water in the DHW tank, moving- on average- 3.4 units of heat for every 1 unit of electricity (i.e. extremely efficient). As explained above, the heat pump has a heat recovery function when operating in cooling mode, where heat removed from the home is used to pre-heat hot water in the tank. This increases the heat pump’s performance by around 52%, i.e. it moves 5.1 units of heat for every 1 unit of electricity. Alongside this, each shower is equipped with a Zypho drain water heat recovery system supplied by Aliaxis, using the heat from wastewater to preheat incoming cold water, reducing DHW energy consumption by between 30% and 50%. The hot water tank and the bathrooms have been located close enough to each other, to avoid the need for a DHW recirculation loop, avoiding the associated heat losses (which then become heat gains in the summer…).

13. Solar photovoltaic generation

Can Naiades will have 18 roof mounted solar PV panels (6,7 kWp in total) installed by Prot Energia, which’ll generate around 7000 kWh/a. This means the home, on an annual basis, will generate around 25% more electricity that it consumes.

14. Water saving

Saving energy is good but so is saving water. During the design phase there was a major drought in Catalonia, so the owners were clear that saving water was also a priority, given that droughts and heat waves are only set to increase over the coming decades. To this end, a series of water saving solutions have been included in the home, to radically reduce water consumption. First up, an Intewa grey water treatment system supplied by Ecospai takes wastewater from showers and sinks, cleans it, and pumps it back to toilet cisterns and to the washing machine. Secondly, low-flow shower heads and taps reduce water consumption. In the first floor bathroom, there is a dry urinal supplied by Alfonso Soto, which precludes the need to use a flush toilet and saves around 4 litres of water that goes down the drain on each flush. Lastly, a rain catchment system collects water for garden watering. There will be no swimming pool, and the garden will include local Mediterranean plant species that don’t need much water.

15. Monitoring & control

The home will be monitored to track energy and water consumption using the Loxone control system, supplied by HEBHAUS, along with MICA indoor air quality sensors supplied by INBIOT and radon gas sensors supplied by Bequerel. Additionally, the Loxone system will be used to control blinds, outdoor lighting, a video intercom, a car charger and the heating, cooling and ventilation system.

The owners would like to thank all of the following people and companies for their support with the project:

Tigges Architekt

Aliaxis

Arquitectura Sana

Bequerel

Ecospai

EGOIN

Energiehaus Arquitectos

Fontalgar Instalaciones

FAKRO

Ventanas Gardea

Griesser

HEBHAUS

House Habitat

INBIOT

Iso Chemie

Knauf Insulation

Loxone

Pafile

Panasonic

Petwalk

Prot Energia

SIGA

Soudal

Zehnder

Dynamic hygrothermal simulation and full-scale validation of a structural insulated panel made from bio-based materials.

praxisadmin on 1 August 2021

Dynamic hygrothermal simulation and full-scale validation of a structural insulated panel made from bio-based materials.

Given the environmental impact of the construction sector- responsible for 40% of the total primary energy consumption of the European Union- reducing both the embodied energy of materials at manufacturing stage and minimising operational energy consumption in buildings are urgent tasks. Timber, agricultural residues, and bio-based materials are local renewable resources that can be transformed into buildings products and components, fomenting the creation of circular economies, and reducing the environmental impact of the sector. The objective of the European ISOBIO project, that ran from 2015 to 2019, financed under the Horizon2020 program, was to address these problems through the development of new insulating materials and renders from plant fibres, agricultural residues, and bio-based binders. The article presents the results of dynamic hygrothermal simulations and full-scale validation of a structural insulated panel made from bio-based materials, for use in the construction of nearly-zero energy buildings.

ISOBIO structural insulated panel for new buildings

The prototype panel measured 1.95m x 1.95m, with a total thickness of 33.2cm in 8 layers with 9 different materials (Figure 1). The panel was rendered external with 25mm of lime and hemp plaster, applied on a rigid 50mm hemp insulation board, mechanically fixed to a 145mm red pine timber structure, filled with hemp, cotton, and flax insulation, followed by a 12mm OSB 3 timber board. An airtight and dynamic vapour control membrane was fixed to the inner face of the OSB, followed by a 45mm service void, insulated between timber battens with hemp, cotton, and flax insulation. The battens were positioned at 90º in relation to the main structural joists to reduce the thermal bridging through the timber. The inner service void was lined with a 40mm thermo-compressed straw board, plastered on the inside with 15mm of composite clay-hemp plaster, applied in 3 layers.

**Figure 1:** ISOBIO panel section drawings and materials

**Figure 2:** Location and type of sensros installed in the panel

**Figure 3:** Panel installation at the HIVE demonstrator, Wroughton, UK

Test set-up

Figure 3 shows the installation of the panels in the demonstrator in Wroughton, UK. A monitoring system was installed, with a meteorological station recording external climate conditions: dry air temperature, relative humidity, solar radiation, wind speed, wind direction, rainfall, and barometric pressure. A temperature probe was installed on the outside of the panel, with a heat flow and temperature probe on the inner face, for measuring thermal transmittance in accordance with ISO 9869 [1]. In addition, temperature and relative humidity sensors were installed at 3 positions within the panel (Figure 2), to measure transient hygrothermal behaviour inside the panel and compare the results with dynamic hygrothermal simulations made with the WUFI Pro tool, following EN 15026 [2]. WUFI Pro 1D is a tool developed by the Fraunhofer Institute in Germany for assessing the hygrothermal performance of one-dimensional building envelope cross-sections, taking into account the moisture content of the materials, their transient hygrothermal performance, capillary transport and summer condensation, with hourly outdoor climate conditions. The software version used was WUFI Pro v. 6.2.1.2210

Data was measured at an interval of 5 minutes, from 24/02/2018 to 14/03/2018 in the HIVE demonstrator, UK, for a total 432 hours, or 18 days, with 5184 data points. The interior temperature was maintained at an average of 25.5 °C throughout the period, with the use of an electric convection heater.

Monitoring Results and Validation

Figure 4 shows a cross section of the modelled panel, with sensor locations. Figure 5 shows the WUFI model of the panel and corresponding sensor locations.

**Figure 4:** Cross section of panel and sensor locations

**Figure 5:** Cross section of WUFI model and sensor locations

Figure 6 shows measured and modelled temperature and RH at position 2 (between the CAVAC rigid insulation and Biofib Trio insulation). Temperature dynamics are well reflected in the model. RH dynamics are less well reflected.

**Figure 6:** Measured vs. modelled (WUFI) interstitial temperature and relative humidity, positin 2, ISOBIO new-build panel, HIVE demonstrator

Figure 7 shows the measured and modelled temperature at position 3 (between the Biofib Trio insulation and OSB board). Temperature dynamics are well reflected in the model, with RH less so. The model nonetheless shows very close alignment with measured results.

**Figure 7:** Measured vs. modelled (WUFI) interstitial temperature and relative humidity, position 3, ISOBIO new build panel, HIVE demonstrator

Figure 8 shows the measured and modelled temperature and RH at position 4 (between the Intello membrane and the Biofib Trio insulation). Temperature and RH dynamics are well reflected in the model.

**Figure 8:** Measured vs. modelled (WUFI) interstitial temperature and relative humidity, position 4, ISOBIO new-build panel, HIVE demonstrator

Figure 9 shows the measured average heat flow rate, compared with the WUFI modelled heat flow rate, showing very good agreement.

**Figure 9:** Measured vs. modelled (WUFI)average heat flow rate, ISOBIO new-build panel, HIVE demonstrator

Conclusion

The results of the measured and modelled temperature and RH show good correlation, with dynamic temperature variations accurately reflected in the model. The short-term variations in relative humidity are not reflected with the same precision in the WUFI modelling results, possibly due to the assumption that the equilibrium water content in the materials is instantaneous, where in reality, there is hysteresis [3]. The hourly measured and modelled thermal transmittance data show very good correlation, with a difference of only 4% over the monitoring period.

The results indicate that bio-based materials combined in a composite SIP panel of this type can offer predictable hygrothermal performance for use in nearly-zero energy buildings.

References

ISO 9869-1:2014 Thermal Insulation – Building elements – in-situ measurement of thermal resistance and thermal transmittance. (Aislamiento térmica – elementos constructivos – medición in-situ de la resistencia térmica y transmitancia térmica)
UNE-EN 15026:2007, Comportamiento higrotérmico de componentes de edificios y elementos constructivos. Evaluación de la transferencia de humedad mediante simulación numérica.(Ratificada por AENOR en junio de 2010.)
N. Reuge, F. Collet, S. Pretot, S. Moisette, M. Bart, O. Style, A. Shea, C. Lanos 2019, Hygrothermal transfers through a bio-based multilayered ISOBIO wall – Part I: Validation of a local kinetics model of sorption and simulations of the HIVE demonstrator. Laboratoire de Génie Civil et Génie Mécanique, Axe Ecomatériaux pour la construction, Université de Rennes, 3 rue du Clos Courtel, BP 90422, 35704 Rennes, France.

Dealing with heat waves: can I use the PHPP to size cooling equipment?

praxisadmin on 10 June 2024

Dealing with heat waves: can I use the PHPP to size cooling equipment?

The issue of correctly sizing cooling equipment is key if we are to maintain thermal comfort, at low power

The article looks at using the PHPP for sizing cooling equipment and compares results with multi-zone calculations using dynamic simulation

Dealing with heat waves: can I use the PHPP to size cooling equipment? — Photo: Energy Vanguard

Given ever more frequent heat waves and the increasing need for active cooling in Passivhaus residential buildings, the issue of correctly sizing cooling equipment is key if we are to maintain thermal comfort, at low power. Over-sizing of cooling plant adds unnecessary cost and energy consumption, increasing stress on power grids as they try and meet peak loads, especially under heat wave conditions. Under-sizing cooling plant will lead to comfort problems, failed expectations and a performance gap that Passivhaus buildings have been consistently shown to fill. Once the work has gone into creating a working PHPP model, can we safely use the tool to size cooling kit?

The article looks at using the PHPP for sizing cooling equipment and compares results with multi-zone calculations using dynamic simulation, based on a simple worked example of a completed and certified Passivhaus residential building in climate zone 5-Warm. The research was prompted by the (painful) lessons learned some years ago, when using the PHPP to size cooling equipment for a single-family low-energy home with Passivhaus components, without adequate modification of boundary conditions. The home had active cooling but suffered from overheating problems and complaints from occupants.

How does PHPP calculate cooling loads?

PHPP calculates sensible and latent cooling loads as the maximum daily average cooling power required to maintain the operative temperature set point, providing an average cooling load across the whole building, based on maximum daily average outdoor air temperature, dew point, sky temperature and solar radiation. Occupancy gains are typically based on a default setting (e.g., for TFA = 150m², occupancy ratio = 51 m²/p, occupancy = 2.9 people.

How does a dynamic simulation tool calculate cooling loads?

Dynamic simulation tools allow for a multi-zone calculation based on hourly climate data, occupancy activity, and equipment operation, providing a time-dependent, high-resolution calculation of cooling loads. Typically, solar gains are calculated on an hourly time-step, and occupancy gains are computed dynamically, such that latent gains increase, and sensible gains decrease, as indoor operative temperature increases (people begin to sweat more as indoor temperature increases…). Is this level of accuracy really necessary, or can we use the PHPP to size cooling plant?

Which kind of tool should I use to size cooling equipment?

Finding the right answer to the question involves asking some the following questions: what building typology are we dealing with? What are the local short-term climate conditions, over 24 hours, during the hottest days? What is the occupancy density of the building, what are the internal heat gains and solar gains, and at what time in the day do they occur? Logically, a single zone, quasi-steady state calculation method such as the one found in PHPP, will be pushed to its limits for larger buildings and/or those with short-term peak gains derived from solar radiation, occupancy or equipment use, particularly if they vary greatly from one zone to the other.

Worked example: PHPP vs. dynamic simulation cooling load calculation for single-family home

Table 1 and Figure 2 shows peak cooling load results per zone, for a single-family certified Passivhaus in Mallorca, Spain, with a TFA of 170m², comparing a dynamic multi-zone calculation using DesignBuilder/EnergyPlus, with PHPP single-zone results. The PHPP climate file for the energy balancing calculations is ES0022b-Palma de Mallorca, but the climate file boundary conditions have been adjusted in the PHPP for the conditions shown in Figure 1 (derived from an hourly data set generated by Meteonorm v.7), with an outdoor air temperature of 38.1ºC and a dew point temperature of 27.2ºC (taken from the average 24-hour relative humidity of 54% @ 38.1ºC dry air temperature). The following adjustments were also made in the PHPP: the occupancy was increased to 10 people, the cooling set-point was reduced to 24ºC, and the solar factor of the glazing was increased by 5% (to eliminate the default soiling factor included in the Glazing worksheet), in agreement with the boundary conditions used in the dynamic calculation.

Figure 1: Climate conditions for cooling load calculation

Figure 2: Results of total cooling loads

The results shown in Table 1 and Figure 2 indicate a negligible 1% difference in the total average peak cooling load results at building level, between the dynamic multi-zone calculation and the PHPP results, suggesting that if the PHPP boundary conditions are modified from those used for building certification, the tool can be safely used for sizing cooling equipment for small residential buildings. This approach has been used on many projects of this type for many years with no complaints of overheating from occupants. However, if we look at peak cooling loads on a zone-to-zone basis, they vary by a + 68% (toilet) and -58% (corridor). While this has generally not been found to be a problem in practice in single-family homes, this suggests caution is required with larger buildings or for zones in smaller buildings with higher short-term peak gains (from solar radiation, occupancy or equipment use). Also, cooling distribution must be carefully planned to ensure specific zones don’t suffer from overheating and sufficient heat is removed from each zone.

Finally, the correct sizing of refrigeration equipment is important for the following reasons:

Oversized cooling equipment leads to higher than necessary energy consumption and therefore increased energy bills.
If cooling power is much higher than necessary, the setpoint temperature is reached earlier and the equipment shuts down (under orders from a thermostat, which only understands temperature, not humidity). This can lead to comfort problems due to excessively high indoor humidity.