Passivhaus Designing for heating load 25th Passivhaus Conference
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Passive solar is dead, long live super-insulation. This paper was presented at the 25th International Passivhaus Conference, online. Passivhaus (Passive House) is the leading international standard for comfortable low energy buildings. This paper recommends designers consider designing for the alternative metric of peak heating load rather than annual energy demand. This means optimising glazing for daylight and views and not for solar gain.
![Design for peak heat load
Passive solar is dead, long live Passivhaus
Nick Grant, Alan Clarke
Elemental Solutions
elementalsolutions.co.uk
@ecominimalnick
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Losses Gains
Heat
flow
[kWh/(m²a)]
Energy balance heating (monthly method)
Non-useful heat gains
External wall - Ambient
Roof/Ceiling - Ambient
Floor slab / Basement ceiling
Windows
Ventilation
solar gains
internal heat gains
heating demand
Heat gains TBs](https://image.slidesharecdn.com/25thpassivhausconferencecompressed-210916060031/85/Passivhaus-Designing-for-heating-load-25th-Passivhaus-Conference-1-320.jpg)
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Passivhaus Designing for heating load 25th Passivhaus Conference
- 1. Design for peak heat load Passive solar is dead, long live Passivhaus Nick Grant, Alan Clarke Elemental Solutions elementalsolutions.co.uk @ecominimalnick 2.0 17.1 17.4 18.0 4.0 0.0 0.0 13.8 0.0 0.0 0.0 6.4 9.1 0.0 16.4 4.8 0 10 20 30 40 50 60 Losses Gains Heat flow [kWh/(m²a)] Energy balance heating (monthly method) Non-useful heat gains External wall - Ambient Roof/Ceiling - Ambient Floor slab / Basement ceiling Windows Ventilation solar gains internal heat gains heating demand Heat gains TBs
- 2. Heating demand or heating load We can choose Warren Benbow Architects
- 3. West facing Trad’ windows Mountain to south
- 4. 8.1 7.4 5.2 15.6 1.2 10.7 17.3 13.1 17.8 0 10 20 30 40 50 60 Losses gains Boiler Int gains Solar gain Vent loss Exterior Door Windows Floor Slab Roof Exterior wall Bushbury School 2010 No Data
- 5. Larch and Lime Houses Ebbw Vale Justin Bere 2011 <15 kWh/(m2.a) 13 kWh(/(m2.a), 11 W/m2 <10 W/m2 17 kWh(/(m2.a), 10 W/m2
- 6. Warren Benbow Architects Heating demand or load, do we need to choose?
- 7. Classic passive-solar Passivhaus Warren Benbow Architects
- 8. Energy balance, gains dominate ? ?
- 9. Passive solar (b. 1940, d. 1979), long live superinsulation Hot in summer, cold in winter
- 10. Passivhaus is not passive-solar but old habits die hard Bigger windows, thicker insulation? • Not cost effective • More embodied carbon • Summer discomfort • Orientation crucial
- 11. Dempsey Decourcy Architects South gable faces neighbour West facing plot challenge
- 12. Kitchen/dining looking west and east Forced us to optimise the glazing for summer comfort Dempsey Decourcy Architects
- 13. 2.0 17.1 17.4 18.0 4.0 0.0 0.0 13.8 0.0 0.0 0.0 6.4 9.1 0.0 16.4 4.8 0 10 20 30 40 50 60 Losses Gains Heat flow [kWh/(m²a)] Energy balance heating (monthly method) Non-useful heat gains External wall - Ambient Roof/Ceiling - Ambient Floor slab / Basement ceiling Windows Ventilation solar gains internal heat gains heating demand Heat gains TBs Dempsey Decourcy Architects Struggled to hit 15 kWh/(m2.a) n50<0.1, negative thermal bridges etc
- 14. How to get from 17 to 15 kWh/(m2.a)? Already optimised design using our standard construction • All measures are high cost, extra embodied energy, hotter in summer. • Heating costs €150/year so might save about €18/y
- 15. 2.0 17.1 17.4 18.0 4.0 0.0 0.0 13.8 0.0 0.0 0.0 6.4 9.1 0.0 16.4 4.8 0 10 20 30 40 50 60 Losses Gains Heat flow [kWh/(m²a)] Energy balance heating (monthly method) Non-useful heat gains External wall - Ambient Roof/Ceiling - Ambient Floor slab / Basement ceiling Windows Ventilation solar gains internal heat gains heating demand Heat gains TBs Dempsey Decourcy Architects Net gain Net loss Compare with heat load balance Losses similar, gains very different Optimise glazing Maximise glazing
- 16. What if we can face the same building south? • Summer comfort even better • Save €18/year on heating! (The occupants are really happy with the east-west orientation)
- 17. + €60/year for heating for a 170m2 house (compared to 15 kWh/(m2.a)) What if we move it to Scotland? Same house, still facing west @ 200m altitude, meets PH!
- 18. Some advantages of designing for peak load • Less sensitive to solar gain; • shading, orientation, location, climate data accuracy, weather, fenestration etc • Doesn’t encourage too much glass! • Good airtightness and ventilation is rewarded (very economic) Lower cost, better comfort, confidence in design pre planning
- 19. Recommendations: • Design for daylight and views not solar gain. • Standardise solutions, tried and tested not bespoke. • 10 W/m2 seems a good target (but we don’t advise heating with air ) UK only?? Please experiment with your projects in your climate
- 20. Power or energy? Thanks for listening
Editor's Notes
- Heating load listed as alternative but may be original. We don’t need to go into that here. Not trying to find the true gospels just to see what works best.
- We have mostly used heating demand except for tricky projects
- Losses all pretty similar, thick insulation. If we reduce the glazing we loose gains, need north classrooms, can’t face everything south. Only option was to crank up the glazing, high g glass. Then tweak night vent to deal with overheating. No peak load data available at the time, much mystery about how this is generated.
- Another example where glazing was maximised to hit the SHD target. Insulation already maximised. Seemed odd that the results would be so different but this was put down to the extreme climate data.
- This south facing example is text book Passivhaus.
- Optimised design, glass not added for gain but for the architecture.
- Design is sensitive to: Internal gains – occupancy, technology, affluence Shading Orientation which we can’t always choose Climate data and microclimate?
- Hot in summer, cold in winter. Very expensive way to heat your building, > 1€/kWh.
- Passivhaus is about superinsulation and demand reduction but obviously the gains are calculated and useful.
- We have been interested in designing for peak load for some time but it always felt like a compromise for tricky sites that struggled to hit the magic 15. This project was a turning point. Lightbulb moment after 14 years of turning the light on and off!
- Daylight optimisation took some work to avoid summer overheating from east and west glazing. Result works really well.
- The proportion of losses are similar when looking at energy and load but solar gain and internal heat gains dominate in the energy balance encouraging us to max the solar gain.
- Remember the early school example
- The proportion of losses are similar when looking at energy and load but solar gain and internal heat gains dominate in the energy balance encouraging us to max the solar gain.
- Will pass on leak load with minor tweak. Facing south and adding glass has less benefit (low summer sun, short winter days) and worse overheating (long summer days).