Mill Creek NetZero Home

Solar Hot Water (Part 2)

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The lessons that I learned from the computer model of our solar hot water system are as follows:

  • insulate the pipes leading from the basement to the collectors to at least R6, preferably R10
  • insulate the storage tank to R50
  • install a 1000 litre storage tank
  • install 3 collectors
  • there is extra heat - install a system to harvest it

We bought the collectors, drainback tank, pipe insulation and other knickknacks from Trimline Design Centre just down the road from the Mill Creek NetZero Home. My builder Peter was very impressed with the clever, simple design of the flat plat collectors that Trimline manufactures. Yes, that’s right, they manufacture solar hot water collectors right here in Edmonton!

Overview

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(schematic of the MCNZH solar hot water system)  read more... »

MCNZH - Progress (part 6) - concrete floors, counter tops, drywall, wood burning stove

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(Pouring concrete, main floor, MCNZH)

A lot has been achieved in the three months since my last progress report.  read more... »

Passive Solar Design

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(MCNZH concrete floor being bathed by sun through a 9’x6’ window)

The most important design considerations for cold climate building are insulation, building envelope, and passive solar design. Given our lofty goals for the Mill Creek NetZero Home (MCNZH), we pushed hard to maximize our return on every one of these fronts.

The MCNZH collects 54% of its annual space heat through passive solar design – that’s 8747 kWh or 31.5 Gigajoules. It does so by:

  1. having huge south windows that are specially manufactured to maximize solar heat gain
  2. containing a large amount of thermal mass to absorb the solar heat when the sun shines
  3. having movable solar awnings that allow 100% of the sunlight to hit the windows during the heating season (the awnings are strictly speaking not a passive part of the solution).

I’ll discuss the first two bullets on this list, given that I’ve already described the movable awnings at length.  read more... »

Wood Burning (part 2)

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A Scan Andersen 10 woodstove, installed in the MCNZH.

People commenting on a recent national CBC article about Edmonton’s NetZero Energy houses spent a lot of effort criticizing the fact that the Mill Creek NetZero Home (MCNZH) has a wood burning stove. Besides proving beyond a doubt that the only thing worse than an ignoramus is an anonymous ignoramus, the comments taught me a bit about what messages to send in a sound bite culture such as ours.

For the record, the MCNZH will consume net zero annual energy without taking the wood burning stove into account. Even if we never burn a fire, the house will consume about 8000 kWh of electricity per year and its PV modules will produce about 8000 kWh per year.

Our Scan Andersen 10 wood stove has been installed, and we really love the quality of warmth that it radiates. Our source of wood will be construction waste from renovation projects in the neighbourhood. If we heated only with wood, here’s how big a pile the MCNZH would use annually:

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A pile of tightly packed construction waste this size will heat the MCNZH for one year.

The pile is 1500 litres in volume, and it represents two thirds of a cord of wood (the cord would be 30% bigger because of the extra spaces between split firewood). We’ll be able to burn the wood very cleanly, because the stove is surrounded by the thermal mass of the concrete floors and a brick mass wall that will installed behind it. A quick clean hot fire will radiate heat into the mass, which will slowly release it into the house for hours afterwards.

Because the heat from the fire will be displacing electric heat from our baseboard heaters, we will in effect be converting construction waste into electricity. The wood stove should make the MCNZH a net electricity exporter of 2000-2500 kWh per year. Because the construction waste wood would have rotted in a landfill anyway, I consider it to be completely carbon neutral. That’s good for the environment, and wood heat provides a good deal of the resiliency that the times ahead will demand.

(cross posted at raisingspaces.com)