Formación

LILU´s House: bio-based Passivhaus

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

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Passivehaus, Blower Door

LILU´s house: bio-based Passivhaus

Description

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

The home has 143 m2 distributed over 2 floors, it will be the headquarters of the company House Habitat and a research unit for companies and universities. It is in the process of Passivhaus Plus certification.

Praxis has delivered the PHPP modelling, design of the thermal envelope and airtight layer, advice on low-impact materials, analysis and optimization of thermal bridges and construction details, and dynamic hygrothermal analysis of risk from moisture damage with the WUFI tool.

Praxis has also undertaken the Blower Door testing and on-site Passivhaus supervision and quality control.

Year: 2022

Location: Abrera, Barcelona

Services:
Blower Door, Passivhaus

Passivhaus in the Mediterranean? Strategies for keeping cool in a Passivhaus on the beach 

A significant rise in temperatures is expected in the Mediterranean area in the coming years. Therefore, identifying and implementing effective strategies to reduce indoor temperatures in buildings and reduce the need for air conditioning is increasingly important. This article presents the strategies used in the design of a Mediterranean passive house, located at a stone’s throw from the beach in Castelldefels, Barcelona.

Passivhaus in the Mediterranean? Strategies for keeping cool in a Passivhaus on the beach

According to the climate modelling presented in the study “Study on Climate Change and Energy in the Mediterranean” carried out by the European Investment Bank, countries in the Mediterranean basin will experience an increase of between 3ºC – 6ºC in average temperatures between the period 2070-2099, based on the 1961-1990 period.

Figure 1: Climate modelling of the Mediterranean basin; average annual variation of air temperatures in summer (°C), 2070-2099 vs 1961-1990

The need to tackle overheating is addressed directly in the European Directive 2010/31/EU for nearly zero energy buildings (nZEB), which states the following: “Priority should be given to strategies that improve the thermal performance of buildings in the summer. To this end, measures should be promoted to prevent overheating, such as shading and sufficient thermal inertia in the construction of buildings, as well as to improve and apply passive cooling techniques (…)” [2]. This article presents the strategies used to improve the thermal performance in summer of a passive house in a Mediterranean climate. 

Caste study: “Esencia Mediterránea”…passive house on the beach 

The home, “Esencia Mediterránea,” has a useful area of 173m2, over two floors, located about 50 meters from the beach, 3 m above sea level (Figure 2, Figure 3, Figure 4) It has an architectural design very much in line with the Mediterranean vernacular tradition, was designed by Guillermo and Iciar Sen, built by House Habitat, and is Passivhaus certified. 

Figure 2: Satellite image, province Barcelona
Figure 3: Satellite image, Castelldefels 
Figure 4: Ground floor 
Figure 5: First floor
Figure 6: Photo of the home [Source: House Habitat] 

The project team:  

  • Architects: Guillermo Sen, Iciar Sen 
  • Technical Architect: Javier García Garrido – Garcia & Sala Arquitectes  
  • Builder: Pere Linares – House Habitat  
  • PHPP & building physics: Oliver Style, Bega Clavero  
  • HVAC design: Vicenç Fulcarà – Progetic 
  • Passivhaus and Blower Door Certification: Micheel Wassouf, Martín Amado – Energiehaus 

Passive cooling strategies 

Many of the strategies used to improve the summer performance of the home are rooted in traditional Mediterranean vernacular architecture and combined with modern solutions. For the thermal analysis presented here, a PHPP model of the house was prepared to meet the minimum requirements of the Spanish Building Code (CTE). Subsequently, the impact of each strategy on cooling demand is presented, until the limiting cooling demand value required by the Passivhaus standard is achieved. 

Shading analysis 

In order to be able to more accurately check the impact of design strategies for the summer, a shadow study was carried out with the DesignBuilder – EnergyPlus thermo-dynamic tool(Figure 7, Figure 8, Figure 9). The results were used to calculated shading reduction factors for each window, that were later introduced in the PHPP shading tab. 

Figure 7: Tree canopy
Figure 8: Dynamic model for shading analysis 
Figure 9: Dynamic model for shading analysis 

Thermal inertia and natural night ventilation 

Combining thermal mass with natural cross ventilation is a key Mediterranean passive cooling strategy. Cooling power is logically limited when minimum night-time temperatures are not sufficiently low (< 18 ºC), so the strategy tends to work best in climates that are inland and at a higher altitude than coastal areas. While lightweight Passive Houses in warm climates have shown good summer performance [3, 4], some thermal inertia, in combination with night ventilation, clearly helps to modulate indoor temperatures and dissipate heat, improving comfort conditions and reducing cooling energy consumption. The house in question was built with a lightweight timber system – inherently low inertia. To incorporate some mass and enhance the effect of natural night ventilation, a 5 cm of mortar layer with ceramic floor tiles were installed on the floors of both floors, providing a specific capacity of 85 Wh/K·m2 inertia (compared to a very light building of 60 Wh/K·m2). With tilt-and-turn windows partially opened at night, a minimum night ventilation air change rate of 0,8/h was calculated with the PHPP tool, provided by simple, cross and stack effect ventilation. 

Reflective surfaces: walls and roofs 

White painted walls and roofs are another feature of traditional Mediterranean architecture. The house has a white silicate mortar render, with a white roof, both with a solar absorption factor of α = 40 % (black α = 95 %). This helps to reflect more solar radiation and reduces transmission heat gains to the interior of the house. 

Shading devices and solar control 

Solar gains are reduced with balconies set back from the façade, exterior shading devices, and solar control glazing with a solar factor of 36%.

Thermal insulation 

Thermal insulation reduces transmission heat gains, especially through roofs. It is important to find a balance between the insulation thicknesses needed for winter and summer, since an excessive thickness of insulation can in some cases prevent heat dissipation at night in the summer. On the ground floor, 15 cm of wood fibre insulation was used, U = 0.264 W/m2·K. On external walls, 20 cm of wood fibre insulation was installed between the timber structure with 6 cm of external high-density wood fibre insulation, U = 0,158 W/m2·K. The roof has 26 cm of wood fibre insulation, for a U = 0,152 W/m2·K 

Air infiltration 

Reducing air ex/infiltration is a strategy that comes from cold and temperate climates, where the priority is to reduce winter heat losses, when there can often be an indoor-outdoor ΔT of 30 ºC. Outdoor air temperatures would have to be 55 ºC to have the same ΔT in summer. However, reducing air infiltrations in coastal Mediterranean climates with high humidity can help reduce latent cooling loads when active cooling is on and windows are shut. In the case study home presented here, reducing air infiltration from n50 = 5 ach (a typical value for newly built homes) to n50 = 0.4 ach, the latent cooling load is reduced by 39% and the latent cooling demand by 7%. 

Mechanical ventilation with heat and moisture recovery (enthalpy) + automatic bypass in summer 

Mechanical ventilation with heat recovery (MVHR) is another solution that originated in central and northern Europe. Does it work in a Mediterranean summer? When outdoor temperatures rise above the indoor comfort temperature (> 25 ºC), users in air-conditioned Mediterranean homes typically close windows and turn on the cooling system, with negative consequences for indoor air quality. A mechanical ventilation system with heat recovery and automatic summer bypass, ensures constant air change and high air quality. When Tout > Tint the heat recovery unit reduces the temperature of the inlet air, shown in Figure 10, where heat recovery reduces the temperature of incoming air from 35.5 ºC to 29.5 ºC:

Figure 10: Mechanical ventilation with heat recovery in the summer  

When Tout < Tint the automatic bypass opens, providing free cooling and bypassing heat recovery. Additionally, an enthalpy unit reduces the amount of water vapor that enters the house in summer when the absolute humidity of the outdoor air is greater than the extract air (which is often the case in warm humid climates in homes with air conditioning / dehumidification). When the air conditioning is off, users can of course open windows at any point.  

Discussion and conclusions 

Figure 11 shows the PHPP simulation results for each of the strategies described above. The reduction in cooling demands from insulation on the roof is less than on the walls – a result that seems surprising. This is due to shading from the tree canopy, which means the reduction is less than in the walls. The results show that the combination of all strategies is greater than the sum of individual strategies. Cooling demand is reduced from 33 kWh/m2·a with the CTE code-compliant building, to 18 kWh/m2·a, meeting the requirements for the Passivhaus certification in a Barcelona climate.  

Figure 11: PHPP simulation results, cooling demands 
 

Combining traditional Mediterranean passive cooling strategies with solutions included in the Passivhaus standard, the summer performance of buildings can be improved with a reduced need for air conditioning.  “Stress testing” your design with a tool such as PHPP in the early stages of the project is essential, and post-construction monitoring and evaluation is highly recommended to learn from mistakes and improve.

References 

[1] Somot, S. (2005), “Modélisation climatique du bassin Méditerranéen: Variabilité et scénarios de changement climatique.” Thése de Doctorat, Université Toulouse III-Paul Sabatier. UFR Sciences de la Vie et de la Terre. pp 347. Toulouse, Francia, 2005. 

[2] Parlamento Europeo (2010), “Directiva 2010/31/UE del Parlamento Europeo y del Consejo, de 19 de mayo de 2010, relativa a la eficiencia energética de los edificios (refundición)”. Parlamento y Consejo Europeo, Bruselas, 2010. 

[3] Wassouf, M. (2015), “Comfort and Passive House in the Mediterranean summer – monitorization of 2 detached homes in Spain Barcelona”, 19th IPHC, Leipizig, Alemania.  

[4] Oliver Style (2016), “Measured performance of a lightweight straw bale passive house in a Mediterranean heat wave”. 20th International Passivhaus Conference, Darmstadt, Alemania. 

Hormipresa Arctic Wall: prefabricated construction system achieves Passivhaus component certification

Hormipresa Arctic Wall is a fully industrialised construction system, certified for passive houses in the warm-temperate climate zone, as the regular U-values of the exterior components are below 0,25 W/m²K and the connections meet the criteria of ‘thermal bridge free’.

Hormipresa Arctic Wall: prefabricated construction system achieves Passivhaus component certification

Hormipresa Arctic Wall is a fully industrialised construction system, certified for passive houses in the warm-temperate climate zone, as the regular U-values of the exterior components are below 0,25 W/m²K and the connections meet the criteria of ‘thermal bridge free’.

The system consists of 9cm of PIR thermal insulation, sandwiched between a 15cm reinforced concrete layer internally and a 6cm white concrete layer externally. The two concrete layers are held together with a galvanized steel lattice system with wall ties that minimise heat transmission while providing mechanical strength. Additionally, 4cm of mineral wool insulation is installed internally in the service void. For the purpose of certification, a three-dimensional simulation was carried out to determine the thermal effect of the steel wall ties and lattice system that penetrate the insulation layer. The roof consists of a prestressed concrete hollow core slab with 14cm of XPS insulation. For the ground floor detail, 8cm of XPS insulation is placed on top of the concrete slab.

For the purposes of certification, a standard passive house window (Uw = 1,00 W/m²K with Ug = 0,90 W/m²K) was used. The overall U-value of the installed window of standard size (1,23 m wide by 1,48 m tall) should be no more than 0,05 W/m²K greater than the Uw to ensure occupant comfort – this criteria is met in this instance. 

Airtightness of the system is achieved in the following way: windows and doors are taped with Iso-Connect Inside Blue Line airtight tapes. The airtight layer of the wall and floor slab is the reinforced concrete layer. In the roof, the airtight layer is the hollow-core slab. Joints between panels and connections with other building elements are sealed with Sikaflex 11-FC elastomeric sealant and painted with Soudal Soudatight SP airtight paint. 

The Passive House Institute has defined international component criteria for seven climate zones based on hygiene, comfort and affordability criteria. In principle, components which have been certified for climate zones with higher requirements may also be used in climates with less stringent requirements. Their use might make economic sense in certain circumstances. 

Check out the Arctic Wall system on the Passivhaus Component database

Many thanks to Soraya Lopez from the Passive House Institute for her considerable efforts to complete the certification process on time.

Casa A, Somió, Gijón: single family home certified as PHI Low Energy Building by Praxis

Casa A, Somió, Gijón: single family home certified as PHI Low Energy Building by Praxis This single-family home is located in Somió, Gijón, Asturias, Spain, and was designed byArchitect Juan Ignacio Corominas, and certified as a PHI Low Energy Building by Oliver Stylefrom Praxis. Patricia Borràs was the Passivhaus Designer on the project. Outer walls …

Casa A, Somió, Gijón: single family home certified as PHI Low Energy Building by Praxis

This single-family home is located in Somió, Gijón, Asturias, Spain, and was designed by
Architect Juan Ignacio Corominas, and certified as a PHI Low Energy Building by Oliver Style
from Praxis. Patricia Borràs was the Passivhaus Designer on the project. Outer walls have 12cm
of external insulation fixed to 24cm honeycomb brick, U = 0.208 W/m2·K. The roof has 28cm of
XPS thermal insulation, U = 0.117 W/m2·K. The walls to ground of the heated basement have
8cm of insulation, U = 0.437 W/m2·K. The suspended floor slab has 15cm of insulation, U =
0.137 W/m2·K.

Window frames are Passivhaus certified Cortizo COR-80, Uf = 0.94 W/m2·K, with low-e argon
filled with triple glazing, Ug = 0.50 W/m2· K and g= 49%. Exterior roller blinds on all windows
control summer solar heat gains. A 9.2 kW Baxi PBM 10 air-source heat pump provides
underfloor space heating, as well as generating domestic hot water. A Passivhaus certified
ventilation unit, Aldes InspirAIR Side 240, provides controlled mechanical ventilation. The
Blower Door test result was N50 = 0.89 ren/h.

Pictures: Juan Ignacio Corominas

Link:

Lessons learned during 10 years of Passivhaus projects

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).

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Figure 1: Form factor vs. insulation thicknesses
Figure 2: Form factor vs. Uw installed

As expected, the results show a clear correlation: the higher the form factor, the greater the insulation thickness required, and the lower the Uwindow. 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

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

Blower Door test in Llerona

Description Blower Door airtightness test to the EN 13829 (A/B) standard for the verification of whole building airtightness, as part of the construction of a single-family home in Llerona, Barcelona. The house is an nZEB designed by Divers Arquitectura. Two tests were carried out: during construction and following completion. For the preliminary test, leaks were …

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Blower Door

Blower Door test in Llerona

Description

Blower Door airtightness test to the EN 13829 (A/B) standard for the verification of whole building airtightness, as part of the construction of a single-family home in Llerona, Barcelona.

The house is an nZEB designed by Divers Arquitectura.

Two tests were carried out: during construction and following completion. For the preliminary test, leaks were detected with a handheld smoke generator and anemometer.

The final result of N50=0,83/h, is well below the minimum requirements of the Spanish building regulations CTE DB HE-1 2019.

Year: 2021

Location Llerona, Barcelona

Services: Blower Door

Blower Door test in Castellgalí

Description Blower Door airtightness test to the EN 13829 (A/B) standard for the verification of whole building airtightness, as part of construction of a single-family home in Castellgalí, Barcelona. The house is an nZEB built by House Habitat. A test was carried out during construction phase, where leaks were detected with a handheld smoke generator …

Praxis cabecera proyecto

Blower Door

Blower Door test in Castellgalí

Description

Blower Door airtightness test to the EN 13829 (A/B) standard for the verification of whole building airtightness, as part of construction of a single-family home in Castellgalí, Barcelona.

The house is an nZEB built by House Habitat.

A test was carried out during construction phase, where leaks were detected with a handheld smoke generator and anemometer.

The final result of N50=1,50/h, is well below the minimum requirements of the Spanish building regulations CTE DB HE-1 2019.

Year: 2021

Location Castellgalí, Barcelona

Services: Blower Door

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.

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.

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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).

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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.

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Figure 4: Outdoor air temperature, Barcelona 3 – 10 July 2015
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Figure 5: Outdoor absolute humidity, Barcelona 3 – 10 July

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.

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Figure 6: System 1, Terrassa, underfloor cooling + dehumidification of ventilation supply air
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.

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Figure 8: System 3, Moià, low-temperature radiators

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.

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Figure 9: System 4, Girona, supply air cooling + recirculation

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.

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Figure 10: System 6, Cardedeu, ducted split units

Thermodynamic analysis of an electric underfloor heating system

The article presents the results of a thermodynamic simulation study, comparing Wood Plastic Composite (WPC) floorboards with ceramic and stoneware floor tiles, heated with an electric underfloor heating system, for both dry and wet assemblies.

Thermodynamic analysis of an electric underfloor heating system

The article presents the results of a thermodynamic simulation study, comparing Wood Plastic Composite (WPC) floorboards with ceramic and stoneware floor tiles, heated with an electric underfloor heating system, for both dry and wet assemblies. The different floor finishes have been modelled in a multi residential building, in Madrid (Spain) climate, using the DesignBuilder-EnergyPlus simulation tool. 

The objective of the study is to analyse the dynamic thermal response of each kind of floor finish, comparing heating energy consumption, peak heating power, floor surface temperature and indoor air temperature. 

Floor types

The Table below shows the different types of floor systems that were modelled:

Figure 1: Floor types and variants included in the analysis

Calculation model

The DesignBuilder tool with the EnergyPlus thermodynamic calculation engine has been used for the simulations.

A multi-residential 4 storey building has been modelled, consisting of 4 dwellings per floor, each with ~ 86 m2 of net floor area, and 342.1 m2 of total heated floor area. The second floor of the building has been modelled for the study, with the floors above and below modelled as adiabatic (they are assumed to be occupied and heated, with the same occupancy and internal heat gain conditions).

Figure 2: Render of the complete building
Figure 3: Render of the calculation model, 2nd floor

The exterior walls are cavity wall with a 14 cm perforated brick outer layer, 5 cm air-void, 6 cm of thermal insulation, and 9 cm of interior hollow brick layer, with 1cm of gypsum plaster (U = 0,39 W/m2·K). The dwellings have aluminium window frames with thermal breaks (Uf = 3,6 W/m2·K) and air-filled double glazing (Ug = 2,9 W/m2·K & g = 69%). The dwelling have mechanical ventilation with an average air change rate of 0.63 ach, with sensible heat recovery that has a efficiency rate of η = 70 %. For dwellings, air infiltration has been calculated as N50 = 5/h, converted to atmospheric pressure and applied to each zone according to its exposed area. Common areas, as the staircase, air infiltration have been modelled with 1 ach of air infiltration.

The energy consumption of all 4 homes on the second floor has been analysed, with a detailed analysis of Room 1 (oriented to the southwest).

Electric radiant floor system

An electric radiant floor system has been modelled. Heating mats with the following nominal power capacities were simulated under each type of flooring:

  • Wood Plastic Composite (WPC) floor (direct system): 75 W per linear metre
  • Wood Plastic Composite (WPC), with self-levelling mortar screed: 116 W per linear metre
  • Stoneware/ceramic floor, with self-levelling mortar screed & gypsum plasterboards: 116 W per linear metre

The radiant floor power for each home and for Room 1 is shown in the following table. The radiant floor has been modelled as “ZoneHVAC: Low Temperature Radiant: Electric” and inserted into DesignBuilder using an EnergyPlus script.

Figure 4: Radiant floor capacity per dwelling

Temperature setpoints

The heating setpoints are those indicated in Annex D “Operational conditions and usage profiles” of the Spanish Building Regulations CTE DB HE 2019:

  • Main setpoint: 20 ºC (07:00 – 22:59)
  • Secondary setpoint: 17 ºC

Results

The 3 periods shown in the following table have been analysed:

Figure 5: Analysis periods

The following parameters have been analysed:

  • Heating consumption [kWh]
  • Maximum capacity of the radiant floor heating mat [kW]
  • Floor temperature [ºC]
  • Indoor air temperature[ºC]

Dry installation: thermal transmittance, thermal resistance, and internal heat capacity

The Figures below show the radiant floor capacity, total thermal transmittance (according to ISO 69446), thermal resistance of the materials on top of the radiant floor heating mat, and the internal heat capacity of the materials above the radiant floor (according to ISO 13786), for each type of floor, for a dry installation.

Figure 6: Total thermal transmittance, thermal resistance above radiant floor & internal heat capacity per area unit above the radiant heating mat, dry installation
Figure 7: Total thermal transmittance, thermal resistance above radiant floor & internal heat capacity per area unit above the radiant heating mat, dry installation

Wet installation: thermal transmittance, thermal resistance, and internal heat capacity

The following graph and table show the radiant floor capacity, the total thermal transmittance (according to ISO 69446), the thermal resistance of the materials above the radiant floor heating mat, and the internal heat capacity of the materials above the radiant floor (according to ISO 13786), of each flooring type, for a wet installation.

Figure 8: Total thermal transmittance, thermal resistance above radiant floor & internal heat capacity per area unit above the radiant heating mat, wet installation
Figure 9: Total thermal transmittance, thermal resistance above radiant floor & internal heat capacity per area unit above the radiant heating mat, dry installation

Dry installation: 2nd floor, heating consumption, 1st October – 31st March

The Table and the Figure below show the results of heating energy consumption for each type of floor, for a dry installation.

Figure 10: Heating consumption results, dry installation, 1st October – 31st March

The results indicate that the heating consumption of floors 2.1 Stoneware and 2.2 Ceramic with double gypsum fibreboards is 20% higher than in 1.1 WPC (direct system).

Floor consumption 3.1 Stoneware and 3.2 Ceramic with 1 dry gypsum fibreboard, is 5% and 4% higher than 1.1 WPC. These differences fall within the margin of uncertainty in the calculations (around 10%).

Figure 11: Heating consumption results, dry installation, 1st October – 31st March

Wet installation: 2nd floor: heating consumption, October 1st – March 1st

The next table and graph show heating consumption results for each floor type, with wet installation.

Figure 12: Heating consumption results, wet installation, 1 October – 31 March

The results indicate that heating consumption of 4.1 Stoneware and 4.2 Ceramic floors with self-levelling mortar screed, are 10% and 9% lower respectively than 1.2 WPC with self-leveling mortar screed. These differences fall within the margin of uncertainty in the calculations (around 10%).

Figure 13: Heating consumption results, wet installation, 1st October – 31st March

Dry installation: Bedroom 1, floor & indoor air temperatures, radiant floor power, and solar gains, January 14th

The evolution of radiant heating mat capacity is shown in the Figures below, together with solar gains, floor surface temperature, and indoor air temperature, during the day of January 14th, for each floor type, for dry installation.

Additionally, the maximum capacity of the radiant heating mat, the time at which maximum capacity occurs, and the maximum floor surface temperature (before the effects of solar radiation) are shown.

The heating setpoint and setback temperatures (20 ºC from 7:00 – 23:00 and 17 ºC the rest of the day) determine when the radiant floor is turned on or off. Solar gains provoke sudden rises in indoor air and floor surface temperatures when the radiant floor is off.

Figure 14: 1.1 WPC, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 15: 2.1 Stoneware, 2 gypsum fibreboards, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 16: 2.2 Ceramic, 2 gypsum fibreboards, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 17: 3.1 Stoneware, 1 gypsum fibreboard, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 18: 3.2 Ceramic, 1 gypsum fibreboard, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 19: All floors, dry installation, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 20: Radiant floor max. capacity, max. floor temp. and time delay, dry installation

The table and graphs above show that the delay between radiant heating mat’s maximum capacity and maximum floor temperatures, is around 4 hours for the 1.1 WPC, approximately 6 hours for stoneware floor and ceramic floor with 2 gypsum fiberboards, and approximately 5 hours with 1 gypsum fiberboard.

This is mainly because the thermal resistance and thermal capacity of the 1.1 WPC (direct system) is lower than with the stoneware and ceramic floors with gypsum fiberboards, therefore takes less time to warm up and transmit heat to the room.

Wet installation: Bedroom 1, floor & indoor air temperatures, radiant floor power, and solar gains, January 14th

The graphs below show the evolution of the radiant heating mat power capacity, solar gains, floor surface temperature, and indoor air temperature, during January 14th, for each floor type, for a wet installation.

The radiant heating mat maximum capacity, the time at which maximum capacity occurs, and the maximum floor surface temperature (before the effects of solar radiation) are shown. For the 1.2 WPC, the maximum floor temperature takes place at 12:00 due to the heat emitted by the radiant heating mat; from that time on, the increase in floor temperature is due to solar gains.

Figure 21: 1.2 WPC with self-levelling mortar screed, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 22: 4.1 Stoneware, self-levelling mortar screed, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 23: 4.2 Ceramic, self-levelling mortar screed, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 24: All floors, wet installation, winter day, radiant floor capacity, solar gains, floor temp. & air temp.
Figure 25: Radiant floor max. capacity, max. floor temp. and time delay, wet installation

The above graphs and table indicate the time delay between the radiant floor’s maximum capacity and the floors maximum temperature, for the WPC, stoneware, and ceramic floor with self-leveling mortar screed, is around 5 hours in all three cases.

Although the heat capacity of the materials above, the radiant floor of floor types 4.1 and 4.2 is far greater than the 1.2 WPC, the thermal resistance of these materials is much lower, so the dynamic response and heating consumption is similar.

Conclusion

The results of the dry installations, indicate that the Wood Plastic Composite flooring has lower energy consumption (between 4% and 20%) and a slightly faster thermal response. In the case of floors with wet installation, the results indicate that the Wood Plastic Composite flooring has a slightly higher energy consumption (between 9% and 10%) and a thermal response similar to the other floor types analyzed. In both cases, given the margin of uncertainty of the calculation, the difference is minimal.

Porta de la Morera Nursing Home

Description Passivhaus design and consultancy for an elderly people’s residency located in Mollet del Vallès. This 8,400 m2 building, designed by Genars and developed by FIATC Seguros via FIATC Residencias (Inverfiatc), is in the process of Passivhaus Classic certification. Praxis has delivered the PHPP modelling, design of the thermal envelope and airtight layer, advice on …

Praxis cabecera proyecto

Passivhaus

Porta de la Morera Nursing Home

Description

Passivhaus design and consultancy for an elderly people’s residency located in Mollet del Vallès. This 8,400 m2 building, designed by Genars and developed by FIATC Seguros via FIATC Residencias (Inverfiatc), is in the process of Passivhaus Classic certification.

Praxis has delivered the PHPP modelling, design of the thermal envelope and airtight layer, advice on low-impact materials, and analysis and optimisation of thermal bridges and construction details.

We’ve also undertaken a thermodynamic and daylighting study of the building, using DesignBuilder (EnergyPlus & Radiance), to assess natural light levels and analyse the risk of summer overheating.

Our work has also included an audit of the mechanical and electrical systems, with proposals for improvements and compliance with the Passivhaus standard, to ensure efficient operation and low maintenance costs. Praxis has also undertaken the Blower Door testing and on-site Passivhaus supervision and quality control.

Year: 2021

Location: Elx, Alicante

Services: Passivhaus consultancy, thermodynamic simulation, daylighting analysis, M & E consultancy, Blower Door testing