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.

Prefabricated passive houses, a cornerstone of Construction 4.0

praxisadmin on 26 February 2024

Prefabrication or industrialised construction is emerging as one of the cornerstones of what is known as Construction 4.0. According to the McKinsey Global Institute, the objective of this 4th Industrial Revolution is to ditch obsolete and traditional construction methods and improve productivity by more than 50%, through- among other things- the optimization of resources based on prefabrication, zero waste and circularity.

Prefabricated passive houses, a cornerstone of Construction 4.0

Is it possible to build a prefabricated Passivhaus building? Of course it is!

Prefabrication or industrialised construction is emerging as one of the cornerstones of what is known as Construction 4.0

Spain was the country with the second most Passivhaus certified square metres in the world

Alongside this, we have the growing trend of passive houses, or homes certified to the Passivhaus standard, a voluntary certification seal that prioritises maximum comfort and indoor air quality for users, with almost zero energy consumption. It is characterised by close attention to detail in the design phase and rigorous on site control to guarantee a high construction quality, and is based on 8 principles:

Bioclimatic design
Thermal insulation
Air tightness
Reduction of thermal bridges
Mechanical ventilation with heat recovery
High performance doors and windows
Shading devices
Efficient mechanical & electrical systems

The increase in the number of buildings with Passivhaus certification during the last 10 years is notable, reaching more than 3,86 million square metres of certified floor area in 2024. In 2020, Spain was the country with the second most Passivhaus certified square metres in the world, led by China.

The marriage of prefabrication with the Passivhaus standard seems a logical step to improve construction quality, reduce execution times and increase productivity. Let’s have a look at some of these together.

Prefabrication: What is it and how is it applied to construction?

Prefabrication or industrialization is the mass production, off site, of the construction elements of a building, transferring work that was previously carried out on site to a workshop or factory. It generally includes structural elements and thermal insulation, assembled in a series of modules such as slabs, façade walls, partitions or roofs. These modules are transported to the building site and assembled, like pieces of a puzzle to form the building.

Industrialisation opens up interesting possibilities, such as the off site installation of windows, external shading systems and some services such as electricity, waste water, ventilation or heating and cooling equipment, among others.

Prefabrication: What is it and how is it applied to construction?

Advantages and drawbacks of prefabrication in passive houses

Advantages of prefabrication for passive houses:

Rapid onsite assembly, allowing for quick weather-proofing and protection from rain and wind. This is especially important in timber construction, a material widely used in the construction of passive houses.

Greater precision and build quality, essential for the construction of Passivhaus buildings, above all in relation to airtightness detailing and the sealing of windows and service penetrations.

Less waste on site and a reduced environmental impact.

Optimization of materials, through standardised production and off site assembly, reducing material waste and costs..

Some of the drawbacks:

Detailed design of the project has to be fully complete before manufacturing and before on-site assembly begins, and allows for fewer or no modifications once on site. It should be noted that Passivhaus projects already require detailed design to be complete before beginning construction, and allow for very little on site improvisation anyway.

The time saved in assembling the prefabricated structure on site, is not always reflected in the total execution time of the building. Services, fittings and interior finishes continue to slow construction down.

The size of the prefabricated elements is limited, in width and height, by the size of the transport trucks and the free height on the roads that connect the factory with the construction site.

Is it possible to build a prefabricated Passivhaus building? Of course it is! Below you can find some examples

LILU´s House: bio-based Passivhaus Plus

Passivhaus design and consultancy, for this single-family house in Abrera, Barcelona, designed by architecture firm OMB Arquitectura and built by House Habitat.

Single-family home in Sitges

Single-family home in Sitges Passivhaus design & consultancy, Blower Door Tests, M & E design, Site supervision Description Passivhaus design and consultancy, M & E engineering, and…

Learnlife Eco Hub: Passivhaus learning space

Passivhaus design & consultancy for a pop-up learning hub in Castelldefels, Barcelona, designed by the Learnlife team.

Original article written by Oliver Style and posted at caloryfrio.com

El Niu: Andorra’s Pioneering Passivhaus Plus Certified Building

praxisadmin on 15 March 2024

El Niu edificio Andorra con certificación Passivhaus Plus

In the heart of Andorra, Europe’s 6th smallest state, a groundbreaking architectural marvel named “El Niu” is redefining sustainable living. Meaning “The Nest” in Catalan, El Niu is a testament to innovative design, energy efficiency, and environmental consciousness.

El Niu: Andorra’s Pioneering Passivhaus Plus Certified Building

El Niu is a testament to innovative design, energy efficiency, and environmental consciousness

Nestled 1275 meters above sea level, El Niu accommodates 11 dwelling units across four floors

El Niu: Andorra's Pioneering Passivhaus Plus Certified Building

Passivhaus Plus Certification

El Niu proudly stands as Andorra’s first multi-residential building to achieve the prestigious Passivhaus Plus certification. This accolade, awarded by Passivhaus Certifier Oliver Style of Praxis Resilient Buildings, is a testament to the collaborative efforts of the development team, including Lluis Lopez Castro of Propietats y Gestió and architect Antoni Martí.

Bernabé Rodríguez’s expertise in mechanical and electrical services engineering, coupled with Pere Marcé Coma’s airtightness Blower Door tests, played important roles in attaining this esteemed certification. Months of dedication and meticulous attention to detail, together with countless rolls of airtight tape, have marked a transformative milestone for Andorra’s architectural landscape.

El Niu Andorra's first multi-residential building with Passivhaus Plus certification

High Altitude, High Efficiency

Nestled 1275 meters above sea level, El Niu accommodates 11 dwelling units across four floors. Facing challenging weather conditions, with temperatures dropping below -10 ºC and winds reaching up to 40 km/h in the depths of winter, El Niu will ensure residents remain warm and cozy. This is achieved through a combination of high levels of insulation, thermal bridge-free construction, high-performance windows, excellent airtightness, and a mechanical ventilation system with heat recovery, all contributing to create an impeccable thermal envelope.

Pioneering Heating and Hot Water Solutions

El Niu sets a new standard in energy-efficient heating and hot water systems with the use of Pichler PKOM 4 compact heat pump units for each apartment, supplied by Orkli. These Passivhaus certified all-in-one units provide mechanical ventilation with heat recovery, heating, cooling, and hot water generation. Notably, they eliminate the need for large and energy-intensive centralised heating and hot water systems, addressing sustainability concerns by minimizing energy consumption, while reducing winter heat losses and summer heat gains that can be perilous for overheating.

Innovative lightweight façade systems

The outer walls of the building consist of two distinct light weight steel frame systems: the Passivhaus certified Passivhaus External Wall System by Knauf Insulation, and the Archisol and Promisol systems by Arcelor Mittal. The Passivhaus certification of the Knauf Insulation system guarantees thermal bridge-free construction and added an extra layer of quality assurance. In addition, Knauf insulation used throughout the building is made from more than 80% recycled glass and incorporates the bio-based E-Technology binder, free from added phenols and formaldehydes, protecting both the workers on site and future occupants from harmful emissions.

Passivhaus certified Passivhaus External Wall System by Knauf Insulation,

Airtightness Excellence

Xavier Rodriguez from SIGA provided airtightness technical support, tapes, and membranes. Thanks to the meticulous work of Lluis Lopez and his team, they met the stringent Blower Door test requirement of n50 ≤ 0.6 ach, guaranteeing a draught-free, high-comfort living experience for El Niu’s occupants, irrespective of the external weather conditions.

Solar Power: The Green Finale

El Niu’s commitment to sustainability culminates in a 37.7 kWp solar PV array projected to generate 91% of the building’s energy consumption. This transformative addition turns El Niu into a nearly net-zero energy powerhouse, using approximately 71% less energy than pre-2010 buildings in Andorra. Impressively, it achieves this while emitting only 5976 kg of CO2eq per annum, contributing significantly to the reduction of the building’s carbon footprint.

In conclusion, El Niu represents a paradigm shift in Andorran residential construction, blending architectural innovation with environmental responsibility. As a Passivhaus Plus certified building, it not only provides a haven for its occupants but also sets a precedent for sustainable living in Andorra and beyond. El Niu is more than a nest: it’s a beacon of hope for a greener, more energy-efficient future.

For more technical information, check out our project data sheet here and in the International Passivhaus Database

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.

LILU’s House: the exception that should be the norm

praxisadmin on 1 April 2023

LILU’s House: the exception that should be the norm

Two stories

First story: a client calls me, the self-builder of a home with Passivhaus Plus certification and tells me: “Outside it’s – 4 ºC and inside we’re at 19.6 ºC, with no heating on.”

Second story: a family calls me, recently installed in their newly built home, and tells me: “We’re at our wits end… we’ve turned up the temperature of the underfloor heating to 51 ºC and we’re still cold! We have really high energy bills and we’re just not comfortable. Can you help us?”

Both homes have an energy performance certificate with an “A” rating. Why, in 2023, is the second story still happening? Why, after having made the biggest investment of their lives, with the expectation of living in a comfortable house with low energy bills, are there families going through what this family is experiencing? The second story is all too common. The first story is an exception, that should really be the norm.

LILU’s House: bioPassivhaus Plus

LILU’s House is the home referred to in the first story above, and it really works. It brings together, under one roof, an office, a home, and a research unit on timber construction. Developed by Pere Linares and Montserrat Lucas, the house has a treated floor area of 142 m2 distributed over two floors. Architect Oriol Martínez has created a modern and compact design with carefully designed and protected openings to maximize solar gain in winter and prevent overheating in summer.

The house has a mixed structure of light weight timber and CLT (cross laminated timber), where healthy materials with a low environmental impact have been prioritized. With a fully industrialized construction system that was prefabricated off-site, quality and precision have improved dramatically, with reduced on-site assembly times, less waste, less dust, less noise, and a lower carbon footprint.

LILU’s House aims to be a laboratory for the dissemination of knowledge about timber construction with biobased materials, certified to the Passivhaus standard.

The home is being monitored to evaluate it’s real-life performance, where data is being recorded on indoor CO2 concentration, air temperature, relative humidity, VOCs, energy consumption, and solar PV production. The house has a roof-integrated solar photovoltaic array with 126 photovoltaic tiles and a nominal power of 6 kWp. Each year, the building will produce, on average, 42% more energy than it consumes.

This is LILU’s House: an exception, which should really be the norm.

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.

Radon gas: invisible and lethal. What is it and how to prevent it?

praxisadmin on 14 November 2022

Radon gas is a naturally occurring radioactive gas that can enter buildings. It is currently the second most predominant cause of lung cancer after tobacco.

Radon gas: invisible and lethal. What is it and how to prevent it?

Radon gas is a naturally occurring radioactive gas that can enter buildings. It is currently the second most predominant cause of lung cancer after tobacco. It’s colorless, tasteless and has no smell, and is produced from the natural radioactive decay of uranium, present in many types of soils and rocks.

How is radon gas measured in a building?

Becquerels (Bq) is the measurement of radioactivity. A becquerel corresponds to the transformation or decay of 1 atomic nucleus per second. In the air, radon concentration is measured by the number of transformations per second in one cubic meter of air (Bq/m3).

The national annual average reference level, set out by WHO in its “WHO Handbook on Indoor Radon: A Public Health Perspective”, is 100 Bq/m3. If this level cannot be reached due to country-specific conditions, the level should not exceed 300 Bq/m3.

Radon measuring devices are divided between passive and active detectors, with an uncertainty range of between 8% and 25%, depending on the type of device. The most common devices are usually passive, logically cheaper than active ones, and incorporate trace sensors for alpha particles, or ion electret chambers, to measure radon concentration.

As the concentration of the gas in indoor air can increase significantly in the short term (hours), is recommended to take long-term measurements (for example, 3 months). If the building has a ventilation or HVAC system, it is convenient to take measurements with the system on and off, in both cases for a long period time.

There are low-cost types of equipment such as the RadonEye RD200, or Airthings Wave, shown in Figure 2 and Figure 3.

Figure 2: RadonEye RD200, low-cost radon gas meter [Source: Radonova]

Figure 3: Airthings Wave, low-cost radon gas meter [Source: Airthings]

Radon gas and the Spanish building regulations

In 2019, and for the first time, Spanish building regulations established the scope and requirement of radon gas with a reference level for the average annual radon concentration inside habitable premises of 300 Bq/m3 (triple of what is recommended by the WHO).

Applicable to all new buildings, extensions, changes of use, or refurbishment of existing buildings, the regulations require the following measures, according to the risk area:

Level 1:

Radon barrier between living spaces and the ground
Ventilated air gap between the living spaces and the ground

Level 2:

Radon barrier between living spaces and the ground
Additional protection system:
- Ventilated air gap between the living spaces and the ground
- Ground depressurization system that allows the gas to dissipate from the ground.

The radon gas map of Spain according to the HS6 level 1 and 2 classification is shown in Figure 4.

Figure 4: Map of radon gas in Spain [Source: Institute for Geoenvironmental Health]

How does radon gas enter a building and how to avoid it?

Radon enters a building through the fissures and openings in the envelope, especially in parts of the building in contact with the ground (slabs, basement walls, etc.), where the concentration of the gas is generally higher on the floors above (ground and first floor, etc). This is accentuated in the building during the heating period, where warm air rises, and the stack effect creates air infiltration of air on the lower floors (and exfiltration on the upper floors).

Radon gas entry is reduced and/or eliminated by a gas-resistant membranes, with a diffusion coefficient against radon less than 10-11 m2/s. An example is shown in Figure 5. The barrier must be continuous, taped and sealed at all joints and service penetrations. It is advisable to conduct a Blower Door test during the construction phase to detect leaks and repair them.

In Level 1 areas, as an alternative, it is possible to build a ventilated crawl space between the living areas and the ground, although it is a less safe solution than a radon barrier.

In Level 2 areas, the radon barrier is essential, along with a ventilated crawl space or a ground depressurization system.

The ground depressurization system consists of installing a network of perforated intake ducts, with mechanical extractors that conduct the air to the outside, above the building. This system has the same drawbacks as the ventilated crawl space and depends on a mechanical system.

Figure 5: Radon gas resistant membrane, Ampack Sisalex 871

Although few epidemiological studies have been conducted on the possible link between radon gas in drinking water and the incidence of stomach cancer, a study by Kyle P Messier and Marc L Serre of the University of North Carolina, USA indicates that increases the risk of stomach cancer. Therefore, water becomes a double entry route, by ingestion of contaminated water or by breathing radon gas evaporated from drinking water. Under normal circumstances, the amount of radon inhaled when breathing is greater than that ingested when drinking.

Radon in drinking water can be reduced and/or eliminated by employing granular activated carbon filters, but the filter itself can accumulate radioactivity and should be located outside the thermal envelope (in a garage, for example), taking care of its treatment as toxic waste at the end of its useful life.

Study of the incidence of radon gas in 122 homes in Ireland

Barry Mc Carron, Xianhai Meng, and Shane Colclough conducted a radon gas measurement study on 122 homes in Ireland, 97 Passivhaus-certified homes, and 25 conventional homes (reference). The results can be seen in Figure 6. The average level of radon gas inside the Passivhaus dwellings was below 40 Bq/m3, both on the ground and first floors. However, in conventional homes, the average level was 104 Bq/m3 on the lower floor, and 69 Bq/m3 on the first floor.

The differences clearly show the effectiveness of airtight construction to prevent the entry of radon gas: one of the requirements of the Passivhaus certification is to have a level of air infiltrations n50 ≤ 0.60, verified by an air-tightness test.

But not only this, Passivhaus homes have a mechanical ventilation system with heat recovery, which constantly renews the air, eliminating stale and polluted air, and introducing fresh and filtered air. This can be seen in the graph in Figure 7, where Professor Walter Reinhold Uhlig of the HTW University of Dresden, measured radon gas in a Passivhaus dwelling with a mechanical ventilation system on and off. With the ventilation turned off, in certain rooms the radon level increased to 350 Bq/m3, having remained below 100 Bq/n3 with the ventilation working.

Figure 6: Radon gas measurement results in 122 homes in Ireland [Source: McCarron et al 2020]

Figure 7: Measurement of radon gas concentration in a Passivhaus dwelling, with and without controlled ventilation [Source: Prof. Walter Reinhold Uhlig]

Considering how lethal it is, radon gas has- surprisingly- gone unnoticed among many professionals in the sector, public administrations, and health professionals. Thanks to increased awareness and the update of the Spanish building regulations, it’s an issue we clearly can’t ignore: we need to prevent radon from entering our buildings, and ensure correct ventilation! The empirical results shown above indicate that an air or radon gas barrier, together with a mechanical ventilation system, is a highly effective combination to reduce the entry of radon gas into a building and thus protect the health of users.

Freshen up: active cooling with radiant ceilings in a Passivhaus retrofit

praxisadmin on 8 July 2022

Freshen up: active cooling with radiant ceilings in a Passivhaus retrofit

The article presents an active cooling system using the supply air of the ventilation system with radiant ceiling panels, installed in a multi-residential building in the historic center of Girona, certified Passivhaus EnerPHit – Demand method. For each apartment, the system consists of an air-source heat pump, a mechanical ventilation unit with heat and moisture recovery (MVHR), a coiling coil on the supply air stream, and radiant ceiling panels. Control is carried out with a home automation system, with temperature and humidity sensors in each room. The solution offers both heating and cooling, working quietly and at low temperature, providing high thermal comfort and efficient performance when used with a heat pump. Reliable performance depends on correct system sizing, proper commissioning of the control system and of ventilation flow rates, and user maintenance and replacement of filters in the MVHR units. Systems such as this are not a good solution in homes where windows are open a lot on the summer and are better suited to warm and dry climates with lower levels of humidity.

The building is a multi-residential 6-storey building in the historic center of Girona, certified by Passivhaus EnerPHit – Demand method [Figure 1]. This private initiative – which was the first of its kind in Catalonia – put 4 new apartments of 129 m2 and a duplex of 162 m2 on the market.

Due to local heritage building regulations, insulation had to be installed inside, with some loss of thermal inertia. Active cooling using a cooling coil on the the ventilation supply air is a relatively simple concept which can be cost effective to install. However, thermal power can be limited when temperatures peak. The system presented here combines supply air cooling with radiant ceiling panels, to provide sufficient power to cover peak cooling loads.

The project data and team are shown below:

Certification class: Passivhaus-EnerPHit – Demand Method
Useful / gross floor area: 678 m2 / 1.038 m2
Developer: MBD Real Estate Group
Builder: Busquets Sitja
Architects: López-Pedrero-Roda Architects
M & E Engineering: PGI Engineering
Control/home automation: Progetic
PHPP, Passivhaus design: Oliver Style, Bega Clavero
Passivhaus Certification: Energiehaus Arquitectos

Description and operation of the system

Given space and floor-to-ceiling height limitations, 2 cooling systems were initially considered:

Ventilation supply air cooling only

Ventilation supply air cooling + radiant ceiling panels

The second option was chosen, given that operative temperatures in the summer could not be maintained at ≤ 25ºC using ventilation supply air cooling only. With 19 m2 of radiant ceiling panels (covering around 15% of the ceiling surface area), peak cooling loads could be met, calculated for an outdoor air temperature of 34.1 ºC, with an absolute humidity = 10,5 g/kg [1].

For each apartment, the system included the following equipment:

Heat pump: Daikin EWYQ005ADVP air-water monobloc heat pump (5.20 kW cooling / 5.65 kW heating) [Figure 2]
Heat & moisture recovery ventilation unit: Zehnder ComfoAir550 enthalpic [Figure 3]
Cooling coil: Zehnder ComfoPost CW10 [Figure 4]
Radiant ceiling panels: Zehnder NIC 150 & NIC 300 [Figure 5]
Control system:

1 temperature & humidity sensor per room
1 Loxone mini server [Figure 7]
Various elements providing on/off control of the heat pump, 3-stepped control of the ventilation flow rate, and on/off control of each radiant ceiling circuit and control of water supply temperature to the radiant ceiling panels with a 3-way valve

Figure 2: Monobloc air-to-water heat pump

Figure 4: Coiling coil, silencer, and supply air ducts (prior to insulation of ducts)

Figure 5: Radiant ceiling panels, prior to fixing on non-radiant panels

Figure 6: Infrared image of radiant ceiling panels

In heating mode, the heat pump generates hot water, circulating it through the radiant ceiling panels at a supply/return temperature of 45 ºC / 40 ºC. At the same time, the coil on the ventilation supply air stream heats the air to around 40ºC. The fan speed is controlled to avoid excessively high flow rates, and which can lead to low relative humidity of indoor air.

In cooling mode, the heat pump generates cold water, circulating it through the radiant ceiling panels at a supply/return temperature of 7 ºC / 12 ºC. At the same time, the coil on the ventilation supply air stream cools air to around 15 ºC. The coil also provides some dehumidification of the supply air, lowering the ambient indoor air dew point temperature and preventing condensation on the ceiling panels. In cooling mode, controlling the temperature of rooms individually is not possible given that the cooling coil only works for the entire apartment.

The heat and moisture recovery ventilation unit also helps to increase the relative humidity of the indoor air in winter and decrease it in summer, improving thermal comfort and reducing the dehumidification load that the cooling coil needs to overcome.

With the ventilation flow rate of 0.4 ach (135 m3/h), radiant ceiling panels typically cover – for both heating and cooling – approximately 65% of thermal loads. The ventilation system with the heating/cooling coil covers the remaining 35%.

Radiant cooling systems must have a robust control system, to avoid problems of surface condensation. Temperature and humidity sensors were therefore installed in each of the 5 rooms where the radiant panels were located (dining room, kitchen and 3 bedrooms). The water temperature of the panels is adjusted with a 3-way mixing valve, based on the temperature and humidity data from the sensors in each room, ensuring the panel surface temperature remains above the dewpoint, avoiding condensation.

The control system also modulates the ventilation unit’s fan power, lowering or raising the flow rate depending on the temperature setpoint and dehumidification needs. A schedule prevents the fan from operating as full flow at night, to avoid noise problems. If maximum power is required at night this can be a problem. The control allows you to set different setpoint temperatures according to specific schedules or occupancy rates, for each day of the week.

In its default setting, the ventilation system works automatically with pre-established schedules (with the possibility of manual adjustment by occupants). Figure 8 summarizes its operation:

**Figure 8: Ventilation speeds and schedules**

Conclusions

Cooling with radiant ceilings can offer an efficient solution that adds power to ventilation supply air cooling systems in Passive Houses in the summer. As the system is predominantly radiant and running at low temperature, it provides good comfort and can be more efficient than convective systems. Ceiling panels can be sized to meet heating and cooling loads, which in residential buildings retrofitted to Passivhaus standard means a coverage of between 15% to 30% of the ceiling surface area. This replaces ducted fan-coil or split systems, which take up more space in suspended ceilings, often a limitation in retrofit.

The control system presented here offers a flexible solution at a reasonable cost, with a relatively user-friendly interface. The possibility of visualizing and monitoring data remotely and in real time, facilitates the optimization of the system and helps in terms of preventive maintenance.

Systems such as this are not a good solution in homes where windows are open a lot on the summer and are more suitable for use in hot dry areas, since, in areas of high humidity, the power of the system will be limited depending on the humidity level of the indoor air and the proximity to the dew point. Robust operation depends correct system sizing, proper commissioning of the control system and of ventilation flow rates, and user maintenance and replacement of filters in the MVHR units.

Lessons learned during 10 years of Passivhaus projects

praxisadmin on 1 March 2022

Lessons learned during the design and construction of Passivhaus buildings over the past 10 years in Spain, identifying the importance of the heat loss form factor, along with successes and pitfalls related to thermal insulation, windows, airtightness, ventilation and active systems.

Lessons learned during 10 years of Passivhaus projects

The Heat Loss Form Factor: Keep it boxy but beautiful!

The compacity of a building has a large influence on energy performance, measured by the form factor, which is the ratio between the thermal envelope and Treated Floor Area (Athermal envelope [m2] ÷ TFA [m2]). The greater the form factor, the greater the exposed heat loss area of the envelope per m2 of TFA, requiring higher levels of thermal protection to achieve the same level of energy efficiency. To illustrate the fact, PHPP modelling results from a range of Passivhaus Classic buildings have been analysed, for varying typologies (single-family, multi-residential, offices and nursing homes) across different Spanish climates. The Form Factor has been compared with two parameters: insulation thickness, using an equivalent thermal conductivity of 0.040 W/m·K (Figure 1) and average Uwindow thermal transmittance (Figure 2).

Gráfico, Gráfico de barras Descripción generada automáticamente — Figure 1: Form factor vs. insulation thicknesses

As expected, the results show a clear correlation: the higher the form factor, the greater the insulation thickness required, and the lower the U_window. The results also indicate that other factors also play a part, such as orientation, solar gain, thermal bridges and- to a lesser extent- thermal inertia.

Blower door test: the moment of truth

In timber construction, OSB boards are often used as the airtight layer and vapour retarder. Research by the Passivhaus Institut [Peper 2014] shows a wide range of air permeability between different manufacturers of OSB boards, with 22mm OSB 4 generally showing best airtightness. Table 1 shows Blower Door results in which different grades and thicknesses of OSB were used:

Table 1: Results of the Blower Door test of three lightweight timber frame houses

The sample is very small, but the results suggest that 18 mm OSB 3 is sufficient to achieve an airtightness of n50 ≤ 0.6/h, as long as all joints and connections are well sealed. Taping a plastic sheet to a 1m2 area of the OSB board (not across joints), prior to the depressurization test, can provide a simple and visual means of assessing the air permeability of an OSB board.

Airtightness in sliding windows

Sliding windows are a standard feature in Mediterranean Spanish homes, which can present challenges in terms of airtightness. Lift and slide windows can now achieve Class 4 air permeability, making them suitable for Passivhaus buildings. However, Blower Door test results with three sliding panes have shown to be problematic (Table 2), with the best results achieved at least one fixed pane. If there are several sliding panes, best results were found with the fixed pane in the centre position.

Table 2: Results of the Blower Door test of 3 buildings with sliding window frames.

Heating, cooling, and ventilation, better not together

The experience of using the ventilation system for heating and cooling, whereby a water-fed heating/cooling coil heats or cools ventilation supply air, has been shown to be problematic, above all during summer heat waves, in humid Mediterranean climates in urban settings. Conditioning outdoor air, rather than recirculating indoor air, means that the increase in heating and cooling power is far from linear as flow rates are increased. Also, flow rates are generally small, further limiting heating/cooling power. Despite thermal insulation sleeves on supply air ventilation ducts, long duct runs have been shown to incur large heat losses in heating mode, and large heat gains in cooling mode, meaning that valve supply temperatures at the end of the duct run are often much lower than those used in the calculations during the design phase.

References

[Burrell 2015] Burrell, E.: What is the Heat Loss Form Factor? Searched on September 9th 2019, accessible at https://elrondburrell.com/blog/passivhaus-heatloss-formfactor/

[Peper 2014] Peper, S.; Bangert, A.; Bastian Z.: Integrating wood beams into the airtight layer. Passive House Institut. 2014

Keep cool and carry on: Passivhaus cooling experiences in the warm climates

praxisadmin on 1 December 2021

With rising global temperatures and increasingly frequent summer heat waves, keeping cool in Passive House buildings has become a hot topic.

Keep cool and carry on: Passivhaus cooling experiences in the warm climates

With rising global temperatures and increasingly frequent summer heat waves, keeping cool in Passive House buildings has become a hot topic.

Bad jokes aside, overheating can be deadly: in France the peak mortality rate during the 2003 heat wave was higher than during the first wave of COVID in 2020, shown in Figure 1 [Parienté et al 2021].

Figure 1: Mortality rate in France during 2003 heat wave vs. first wave of COVID 2020
[Source: Parienté et al 2021]

Active cooling in all climates warmer than warm-temperate looks like it will become standard. The question is: for cool-temperature climates, is passive cooling sufficient, or is active cooling unavoidable? What are the pros and cons of the different systems? Will my client ring me up during the next heat wave and give me an ear full?

The article provides technical analysis and lessons learnt from 10 years of experience applying passive and active cooling strategies in residential Passive House buildings in Catalonia, Spain. 6 different kinds of active cooling systems that have been designed and installed in single-family Passivhaus homes are compared, assessing the simplicity or complexity of design, installation, and commissioning; upfront costs; user-friendliness, robustness, and comfort; environmental impact of refrigerants for active cooling systems; and the bottom line: measured performance and monitoring data.

Passive cooling

Careful design, moderately sized and well shaded openings, close attention to local climate, and active users have been found to be some of the key drivers of successful passive cooling. Reduction of internal heat gains is key, with efficient appliances and compact Domestic Hot Water (DHW) systems that avoid the need for recirculation circuits. If recirculation circuits are unavoidable, they need high levels of insulation and flow rate control, with reduced DHW water supply temperatures- so long as this is compatible with Legionella prevention. Ultrafiltration and chemical shock disinfection are promising alternatives to the conventional solution of high DHW supply temperatures and thermal shock prevention.

External shading devices are essential, ideally with motorised external blinds, either user controlled or automated. Even north facing windows in Passivhaus buildings need shading: the very long time constant of Passivhaus buildings mean diffuse solar radiation can cause overheating. If only fixed shading can be used, then appropriate solutions for each orientation are key, with particular attention to east and west facing glazing, which receive more solar radiation in the summer than south-facing glazing (shown in Figure 2). Deep horizontal overhangs on southern glazing work best (or northern glazing in the southern hemisphere), with slanted vertical fins for east and west-facing glazing.

Gráfico, Gráfico de líneas

Descripción generada automáticamente — Figure 2: Solar radiation by orientation, Barcelona PHPP climate file

Natural night ventilation combined with thermal inertia works well when night temperatures are sufficiently low. Cool external colours, high levels of insulation on roofs, ground coupling, and ceiling fans, are also effective strategies. Figure 3 shows an example of measured data for a single-family home employing many of those strategies (but with little thermal inertia).

Gráfico

Descripción generada automáticamente — Figure 3: Collsuspina, passive cooling

Passive cooling is in general simple, low-cost, easy to install, maintain and commission, and can deliver good performance. However, passive cooling strategies are highly climate dependent and rely on careful user behaviour. Where average air temperatures and levels of solar radiation are high (hot ground), minimum night temperatures do not drop below ~ 20 ºC (limited cooling power from natural night ventilation), and night sky temperatures and outdoor air humidity are high, passive cooling won’t work. In this case, active cooling is unavoidable to maintain comfort. Figure 4 and Figure 5 show an example of climate conditions in which passive cooling strategies won’t work, during the 2015 heat wave in Barcelona, Spain.

Active cooling

6 different cooling systems that have been designed and installed in residential Passive Houses are compared, assessing 6 criteria through a simple 1-to-5 point scoring system, shown in Table 1. Monitored data is provided for systems System 1, 2, 5 and 6.

Table 1: Quantitative comparison of 6 different cooling systems

Radiant cooling systems offer a high level of comfort and efficiency, but are more complex to design, install and commission, with higher capital cost. Humidity control and cooling power has been found to be problematic in warm and humid climates, where users go in and out of the house (garden/balcony etc.). Monitored data for an underfloor cooling system is shown in Figure 6. Figure 7 shows monitored data for a radiant ceiling system.

Figure 7: System 2, La Garriga, radiant ceiling + dehumidification of ventilation supply air

Low-temperature radiators (set in the floor, or wall-mounted) offer a reasonable balance between simplicity, cost, efficiency, and comfort, albeit with less cooling power than fan-coils and splits, requiring a greater number of individual units to cover the same given area than a ducted fan-coil/split system (where 1 indoor unit can cool several rooms). Figure 8 shows monitored data for this kind of system.

Supply air cooling has been found to be problematic, due to limited cooling power (a consequence of conditioning outdoor air rather than recirculating indoor air, low flow rates, and heat gain along long duct runs). Power can be increased using partial recirculation but monitored data in Figure 9 shows that temperature and relative humidity often move outside the extended comfort range. The advantages of this kind of system are simplicity and low capital cost, but the limited cooling power means passive cooling measures must be robust: once overheating has set in, the system will struggle to eliminate heat.

Conventional convective solutions through the recirculation of indoor air (i.e., ducted or wall-mounted fan-coil or split systems) have been found to be the most robust. They are generally simple to design, install and commission, have a lower capital cost than radiant systems, and power can be modulated to deal with peak loads. They are less comfortable than radiant systems. Split systems using refrigerant distribution offer greater dehumidification power (due to lower refrigerant sink temperatures than water) with a faster response than fan-coils and water distribution. However, the Glower Warming Potential (GWP) of the refrigerants and risk of leaks from on-site manipulation is an important consideration. Figure 10 shows monitored data for ducted split system. Temperatures outside the extended comfort range are during hours when the home was not occupied, and the clients report a high level of thermal comfort.