During this last session of Passive House Training I learned that 25-35kWh per square meter and year are acceptable, and respectable space-conditioning energy numbers for a remodeled building. At the same time, any other requirements like air-tightness do not differ from the original Passive House requirements. While a remodel that achieves 25-35 kWh per square meter and year does not pass PHPP (Passive House Planning Package) calculations, it is a substantial achievement and definitely a significant improvement over performance before the upgrade (potentially up to 80% and more energy saved).

The Passive House Institute has researched and shown, that there is tremendous value in retrofitting to Passive House standard. Adding Passive House insulation and achieving high air-tightness helps avoid condensation and due-points at the thermal bridges and inside wall assemblies, therefore protecting the existing structure far better than a lesser improvement. This also ensures healthier indoor environmental quality.

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  • Christina Snyder says:

    What to do in a retrofit situation is the number one question I encounter, and it was really encouraging at the PH Consultants Training to hear that even if you can’t get down to the PH standard of 15kwh/sq.m yearly due to structural thermal bridges that can’t be completely mitigated, air-sealing and insulating the exterior of existing buildings to the levels of superinsulation seen in PH buildings doesn’t create problems with moisture and condensation, it actually reduces inherent problems, increases comfort & Indoor Air Quality, and saves a lot of energy & $ operating the building. And as long as you are working on the outside of the structure, the retrofit can be relatively uncomplicated.

    Dealing with situations where you can’t do exterior insulating (typically due to limitations imposed by zoning or historic preservation regulations) is far more problematic and needs special analysis to avoid moisture condensation problems on the many unavoidable thermal bridges that result from this method. But even so, air-sealing and superinsulation can mitigate the condensation and comfort issues caused by themal bridges when done properly. It was really interesting to see the thermal modeling that showed superinsulation around thermal bridges raises the interior temp. of the surface of the thermal bridges, thus lessening the chance of those surfaces being at or below the DEW point of the interior air, thus also reducing condensation events. While I will probably continue to avoid the interior insulation method unless it is a commercial client paying me to carry professional insurance, it was very reassuring to see that it is possible and historic buildings aren’t condemned to be energy hogs for life.

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