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2005 10 19
157 Coxwell, Part 3
It’s the end of February of 2003 and the Coxwell house will be rented soon. The temperature hovers around minus 20 degrees Celsius. A news report indicates there has been power outage in the Coxwell area. Normally this is not a concern except at Coxwell the ‘geo-sewer’ heating is put to the test. You see I’ve married the water supply line with the sewer line from the street encased in an insulation jacket. Sewer gas is always warm and moist. It would keep the water line from freezing without electricity.

imageBuilding codes require a heating cable be attached to the water line for that portion that is not within an insulated interior or four feet below grade in order to prevent freezing. There is no power outage provision for single-family homes. The bridge to the house carries people, water, electrical and sewer stuff: It’s the umbilical cord. This device has several benefits; primarily it allows me to float a pure geometric form from the ground un-encumbered by unsightly tendrils. I had to construct the heat exchanger myself (see picture). It was beyond the scope of the average plumber or mechanical contractor.

It’s estimated that the power has been out for 18 hours. At minus 20 degrees pipes have been bursting in the area. I walk up to the bridge. There are no sounds of gushing water, no waterfall ice sheets. I walk into the house the temperature is 14 degrees above zero. I’ve set it at 17 degrees for when I’m not there. I touch the floor: it cool. I conclude that the heat pump must have come on recently. Anyway, no extraneous noises about. I wait 5 minutes for the floor to warm up. It did. I check under the bridge and house to see if there were any signs of leaking. Nothing. I breathe, relieved.

There is freshness in the air without that burnt/dry scent normally associated with forced air systems or radiators. Heated floors don’t burn the air; they warm it by not exceeding 30 degrees at floor level. Any natural humidity in the air is preserved.

This Coxwell house is, arguably, the first house built since the 1997 edition of the OBC not requiring a heat recovery ventilation system. I pitched the head mechanical engineer at the city. I showed him my calculations for the house’s natural air infiltration and ex-filtration in concordance with non-combusting appliances such as the ‘direct vent’ furnace, condensing dryer, warm floors and single air volume that did not combust any internal air. As such the air exchange rate met the facts and intent of the code. Additionally, anticipating the on-site inspector’s non-familiarity of these principles, that the chief engineer would support these building systems including that of the sewer and water line being in the same insulated conduit and it would pose no danger to freezing or cross contamination. True to his word, the city engineer backed me up when the time came to deal with the on-site inspector.
The wrap up article comes next week.
[email this story] Posted by Rohan Walters on 10/19 at 04:22 AM

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