Heat pumps and hydronic heating for 2600 sq ft Vancouver Island
I’m trying to find more information to further my understanding of sensible heat pump system for a new home build on the west coast of Vancouver Island, British Columbia, Canada.
Our main dilemma is we lack any natural gas so we are obligated to use electricity for our main heating system.
Our plan is to do two levels with both concrete slab infloor hydronic heating for the two level 2600 sq ft total dwelling.
Has anyone had any experience with the Kelowna company Thermo Matrix? http://thermomatrix.com/ It appears that Naikoon Construction just completed Canada’s greenest house through LEED in North Vancouver and used this system within their net-zero design.
Also, is it more practical to go with air sourced heat pump or to go with a air to water heat pump for DHW and hydronic heating.
Any feed back or suggestions would be appreciated!
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Replies
Blake,
If you want to install a hydronic heating system (radiant tubing in your floor assembly), your only choice for a heat source would be the Daikin Altherma air-to-water heat pump. These systems are very expensive.
It's far simpler to install a few ductless minisplit units. You don't really need a radiant floor. For more information, see All About Radiant Floors.
The ThermoMatrix heat pumps would probably do it. I'm a bit skeptical that the full-system COP would actually hit the advertized 4.5 in a coastal B.C. climate, but maybe.
http://thermomatrix.com/thermoproducts/coolfire-heat-pump/
Their smallest ThermoMatrix unit is a three-ton, which would likely be oversized for a high-R 2600' house, but may be about right for a code-min house. Your 99% outside design temp is probably about -7C/+19F, a temp at which the 3-tonner delivers 27,140 BTU/hr. And that is at 120F output water temps, with 110F returns, much higher temps than you would be running in a radiant slab or above-the-subfloor radiant floor system. At lower output temps it's capacity will be well north of 30,000 BTU/hr, and could be even more than twice your actual heat load.
That's enough output to cover the heat load of my ~2400' sub-code 2x4 framed 1920s antique at that temp. A decent new construction build with better windows and higher R all around would be less. But without a heat load number on your design it's hard to really advise. It's possible to build houses that size with heat loads under 15,000 BTU/hr @ -7C without breaking the bank.
http://thermomatrix.com/brochures/2014/heat-pumps/3-ton-double-split.pdf
Most radiant floor systems are going to be substantially more expensive than just designing & building the heat load down to much lower levels than the output of a 3-ton ThermoMatrix.
Air to water heat pump systems are going to be a lot cheaper to do than ground to water or water-to water in most situations. If you have a large pond or lake next to the house to use it may work out cheaply, but the system performance is only as good as the system designer.
Air-to-air is more straightforward, and can work well in your climate. Ducted air-to-air systems can even work, but here again you are a bit dependent on the quality of the duct design & implementation. Ductless air to air systems such as mini-splits re harder to screw up, (once you have the sizing right), but room to room temperature differences can go off the rails if you aren't careful in your house design.
Before designing any heating system, the first order of business is to calculate the heat loads of each room, as well as the whole house. On new construction you have a great deal of flexibility on both individual room & whole house heat loads, since it can all be adjusted by he details of the design.