Residential Renovation of a Schoolhouse

A Deep Energy Retrofit
June 2010 Update -- 2nd Winter


The material below is Gordon's report on how things have been going in their energy retrofit of a schoolhouse into a very energy efficient home after 2 full winters.   Gordon gives a summary of the thermal performance to date, as well as some fixes to minor problems with the retrofit. 

Note that in addition to the 2 year report below, Gordon has provided an updated copy of the thermal analysis spreadsheet...


I'd like to thank Gordon and Sue once again for the great energy retrofit and for the excellent documentation!


A lot of homes use more space heating energy per month that Gordon's home uses per year!


For the full story on the original project...


1.  Schoolhouse Deep Energy Retrofit – June 2010 Update:

 The logging of space heating requirements for the schoolhouse has been completed for the second winter (to the end of May 2010).  As an attachment, an .xls spreadsheet is provided as a  replacement for the previous thermal analysis.    A number of corrections to minor errors have been made, so some values have changed – but nothing significant.  
 The updated thermal analysis spreadsheet is here...

Our space heating costs were significantly lower this (second) winter.  The cost breakdown was $7 for electricity, $ 13 for LPG, and $ 199 for firewood, for a total heating cost of  CA$ 219.  We are pleased.   

Until this last winter, eastern Canada has been slow to show global warming trends (as opposed to the major warming trends of the artic and northwest Canada).  However, winter 2009/2010 was indeed significantly warmer than ‘normal’.  At first glance, one would expect that our purchased net space heating   would have been somewhat less than our modeled expectations for the ‘average winter’.  For residents of typical dwellings, this would have been certainly so.  The space heating requirement was actually slightly higher than expected in our case!   

In our typical winters, cloudy days are about 1 in 3.  October and November are quite cloudy, but seldom cold.  The sky is predominantly clear through the cold stretches of January to March.  Solar heating is great for this situation.   However, this last winter was very different.   

Over-all, it was a little more cloudy.  There were more days of heavy ‘socked-in’ cloud.  There seemed to have been numerous extended periods of heavy haze (somewhat bright, but poor opportunities for significant harvesting of solar heat) – which is not common in this area.  The really surprising thing was that extended periods of full sun were rare.  It was exceedingly common for sporadic cloud cover to interrupt full sunshine within 10 minutes or so.   For the period of 15 January to February 27, the solarium heater never got hot enough to trip the blower to the house (Usually we expect that blower to operate six to eight hours nearly every day).  It was a winter that seemed bright enough - not sufficiently gloomy to be depressing - but was far from ideal for solar harvesting.  I think we now have a better appreciation for the European winter climate, and why, the PassiveHaus Inst. favors insulation over insolation.  We now appreciate the clear sky of winters past.   

This type of winter highlighted a difficulty with our homebuilt pyranometer.  It is based upon an electrical hour meter with a near instantaneous, tenth of an hour trip  The threshold was set at about 2 stops down from bright sun, which is about 25% of full sun energy.  The logic was that if it were above about 25%, some energy could be harvested (and should be recorded in logs).  It is now realized that the official calibration dates from sunshine through a lens, burning a paper trace - which of course requires very close to full sun intensity.  In a climate with a predominance of either clear sky or heavy cloud, the sensitivity of the threshold matters little, when comparing one’s own measurements with climate ‘normals’ – such has been our situationThis last winter we ’logged’ about 75% of the typical insolation, but I doubt whether we actually surpassed 50% when one considers both the extent of haze and the subtle difference in the tenth of hour sampling interval. 

 I should also mention that we a very pleased with the modifications we made to the vent, stack and HRV inlet.  These areas are noticeably warmer in mid-winter. 

Best wishes


June, 2010