[Greenbuilding] Sustainable Home Heating Systems (Ross MacLeod)

[Paul Eldridge]

For a simple, reliable, and economical secondary heat source, you might 
also consider a mid or high efficiency ductless heat pump.  A ductless 
heat pump with a HSPF of 8.5 (zones IV and V) would effectively provide 
2.5 kWh of heat for every one kWh of electricity and with new R410A 
refrigerants, advanced defrosting controls and more efficient inverter 
drives, many newer models continue to operate all the way down to -15C 
(5F) and even -20C.

My two year old, 14,000 BTU/hr Friedrich unit (7.2 HSPF) has cut my 
space heating costs by more than half.  I pay an average of 4.3 cents 
per kWh(e) for the heat it provides versus 9.7 cents for that of my 82% 
AFUE oil-fired boiler, and since I purchase 100% green power through 
Nova Scotia Power, my net GHG emissions are theoretically near zero.

I paid $2,100.00 for my system, installed.  By comparison, a name brand 
pellet stove, hearth pad, vent kit and installation might very well cost 
twice that.  In addition, pellet stoves require a thorough annual 
cleaning (budget approximately $150.00/year for a technician to perform 
this service) and the venting should be cleaned about every 50 bags 
(homeowners can do this with a pellet brush and flexible rod).  Their 
reliability can be hit and miss; my family business sells them and, 
based on what I know, I wouldn't personally own one.  Also bear in mind 
a cloud of fine dust is released into the air every time you refill the 
hopper, so anyone with asthma or respiratory issues should proceed with 
due caution.

In terms of operating cost, a 40-pound bag of good quality wood pellets 
currently retails for about $4.70 in the Halifax area.  Assuming 80 per 
cent combustion efficiency, a bag of pellets provides roughly 80 kWh of 
heat (net), which puts its operating cost per kWh in the range of 5.9 
cents.  On this basis, a heat pump with a HSPF of 8.5 would be the more 
economical alternative in areas where electricity retails for 14.5 cents 
per kWh or less.  Plus there's no need to purchase, store and haul about 
a tonne or more of pellets each year (and in the event of a fire, that's 
a lot of extra fuel to have hanging around).  With a ductless heat pump, 
all you do is press the power button on the remote and select the 
desired temperature.

One other advantage: unlike pellet stoves, ductless heat pumps provide 
both heat and coolth, so they perform useful service all year round.  
Here in Atlantic Canada, we don't require much in the way of cooling, 
but we seemingly run our dehumidifiers non-stop between April and 
October.  I operate my heat pump in "dry" mode, which extracts excess 
moisture without overcooling the air.  It uses considerably less 
electricity than my Energy Star dehumidifier and it doesn't dump its 
waste heat inside the thermal envelope, which makes for a more 
comfortable living space during the summer months.

Best regards,
Paul

>I am looking at retrofitting a home in Eastern Canada to be more energy
>efficient, and to employ a more sustainable heating system.  I am addressing
>the 'envelop' first but there are practical limits to how efficient I can
>make it in the short term.
>
>Given climate, cost, and reliability issues with the future use of Natural
>gas to heat homes, and the critical nature of heating in a cold environment
>like ours, I am looking for a reliable long term source of space and water
>heating.   I am planning to use solar thermal to be the primary source of
>water heating, but debating the short and long term benefits of high
>efficiency wood stoves versus biomass pellet stoves for space heating.
>
>On the positive side of biomass pellet stoves:
>
>   - they can burn pellets made from various biomass materials including;
>   wood, switchgrass, corn ... so that you should have a reliable supply over
>   time
>   - the fuel is very cost effective today, and compares favourably with
>   other sources (superior to wood stoves)
>   - they are environmentally friendly
>
>On the negative side:
>
>   - today the fuelling process is not very convenient and requires
>   frequent refills during the depths of winter
>   - relatively high maintenance due to chinking
>   - requires electricity to operate the augers and fans that are
>   essential for it to work.   As a result, they are generally not as reliable
>   as wood stoves
>
>Does anyone have any related insights, or knowledge of recent innovations
>that might influence the outcome of my assessment?
>  
>