Zero Heat-Energy Building?

hallwayWell maybe not quite…but our No-Winter-Heat experiment at The Blockhouse School has revealed something truly amazing – our 50+ year old unheated building’s interior does not go down to freezing temperatures even in a normally cold Maritime Canada winter!

In fact, on sunny days there is enough passive solar on the south side to raise temperatures to the mid-teens Centigrade, quite passable for working in one of those rooms, though longjohns are advised.

I have to wonder if the building’s designers of 50 years ago even realized this? Normally large institutional buildings get built and then the heat is turned on and never turned off, so no one would know what the buildings would be like without heating.

I think that the thick concrete slab foundation has a lot to do with this phenomena. And perhaps the ratio of exterior exposure to the building’s internal volume and surface area of the slab are part of the secret.

Open windows in August

Open windows in August

Another factor is use. Normally, schools are closed up for much of the summer. In our situation the summer was our most active time and we intentionally kept many windows and external doors open to let in fresh warm air. That alone raised the temperature of the slab which stored a good deal of the summer heat in its 15,000 sq ft, even on the not-so-sunny sides of the structure.

Then as fall settled in the floor began giving its heat back to the cooling internal air. Late summer and autumn internal temperatures remained quite constant, in the low teens, right up until Christmas!

Once most of the summer’s stored heat has come out of the floor to heat the interior air, the deep ground-heat of the earth under the slab, which is a pretty constant 9-10 degrees Centigrade, keeps the temperatures from dropping lower. Again there seems to be just enough floor area and semi-insulated wall & roof area to make this work.

Truth window in book-insulated wall

Truth window in book-insulated wall

Our preliminary experiments with used books and straw bales coated with earthplaster as interior retrofit insulation, suggests that with these low-cost means we could keep even more free summer heat in the building.

Then there is the opportunity of the reverse option. During the summer 2012 heatwave, which made outdoor work really challenging, we noticed that the building’s interior stayed very pleasant. The floor was sucking up that heat and making the interior air much cooler than outdoor air. Wow, free air-conditioning! This spring we will isolate a small section of floor using straw-bale and bookwalls to create an experimental coldroom for storing vegetables. With some luck in
getting our floor-area to room-volume ratios right, and good ventilation, we may be able to use free cooling to keep vegetables in good condition for most of next winter. Stay tuned!

David Cameron
Projects Coordinator

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