|This home's mechanical system combines
forced air circulation with solar energy with energy from a wood-fired
boiler in a hybrid system which uses a tank with multiple heat exchangers.
The hot water storage tank contains 450
liters and has three internal heat exchangers:
A high efficiency propane-fired DHW tank provides
back-up to the hybrid system.
lowest heat exchanger, 24 ft long of double wall construction, is connected
to the solar heat source, a solar collector on the roof
the middle heat exchanger, 20 ft long, is
connected to the wood stove heat source
and the top heat exchanger, 30 ft long, delivers
on-demand heat to the forced air distribution system for space heating.
The residence combines solar and wood stove
energy gains with the double drywall thermal mass. The output of the hot
water storage tank is integrated with tempered incoming well water. There
are two wells on the side of the tank, one for a temperature gauge and
the other for an aquastat. Solar energy feeds the lowest heat exchanger
because energy from the sun is not as hot or as dependable as heat from
a wood-fired boiler.
The wood-fired boiler is used when the
outside weather requires space heating indoors. There is increasing interest
in hybrid systems combining space and water heating.
We've addressed the building load with
conservation from a manufactured "single wall" stud (R50), a continuous
air and vapour barrier (0.85 ach @ 50 pa) and high efficiency fiberglass
windows. The windows are triple glazed, low E, argon-filled with non-conductive
edge spaces. The hybrid system is incorporated to supply the heating.
The forced air circulation is distributed
through a "with-in" floor system: air is forced through the floor cavity
by using open web manufactured floor joists. This results in both
radiant floor and ceiling heating with forced air distribution that also
circulates ventilation air from a heat recovery ventilator.
Further environmental loads are reduced
by the use of low energy appliances and lighting, low flow fixtures and
appliances, low tox construction materials and finishes.
An alternative septic system was considered
that provides better treatment of the waste from the building, but at twice
the cost it proved too expensive.