Hello, I've made a heat loss calculation from builditsolar.com and came in at 32645 btu/hr in january. This is for a double stud wall house with two 1200 sqft storey. Using this, I would only need 10kw of baseboard to heat the whole house and it's really under the rule of thumb ( 10W per sqft). Does this make sense to you or is it really too low and I should add more baseboard than this? thanks Alexis

I've had an analysis done using REM Rate for a double wall 2600 SF house, came in at 28000 btu heating load, so your calculation is plausible, all other things equal. What is the rest of your insulation and what climate zone? I'm using minisplits; least expensive & most efficient for what I'm building.

I'm in quebec, january mean temp is -13F. The ceiling is insulated with R50 cellulose, slab to r10 ( 6ft underground) and basement wall to r20.

I would love to use only one minisplit but I still need a backup heat source so I don't have money right away to pay for two heating source. I'm installing baseboard heater and will upgrade to a mini split in the future...

thanks

Alexis

I'd suggest upgrading your ceiling to R60 or 70, and increasing the slab and foundation insulation. You can do or have done detailed calculations which will tell you what the change in heating load is, and ou might find that it will be worth doing. Your climate is marginal for minisplits since the Mitsubishi hyper heat shut off at -15o.

Posted By Bob I on 17 Sep 2013 01:37 PM
I'd suggest upgrading your ceiling to R60 or 70, and increasing the slab and foundation insulation. You can do or have done detailed calculations which will tell you what the change in heating load is, and ou might find that it will be worth doing. Your climate is marginal for minisplits since the Mitsubishi hyper heat shut off at -15o.

I thought the H2i units didn't shut down until -28C/-18F, and automatically turn back on when it warms UP to -26C/-15F (?).

But that's Mitsubishi. 

The Fujitsu " XLTH" (eXtra Low Temperature Heating) AOU-xxRLS2-H series are have fully rated outputs at -15F, and continue to chug away at even lower outdoor temps, as do the -xxRLS2, not-H series.  The -H versions have features specifically designed for managing extended cold weather operation that the others do not,(eg: an intermittent pan heater for clearing frozen defrost water before it rises high enough to damage the blower)  and would the preferred mini-split for areas that drop to -28C or lower since it doesn't need to stop to self-protect the way the Mitsubishi H2i Hyper Heating units do.

Even thought the BuilditSolar heat load calculator is about as crude as they come, 10kw IS a plausible number for that house.

Rather than baseboards, use radiant cove heaters mounted near the top of the walls, just below the ceiling. They are comparable in cost to baseboards, but unlike baseboard they don't get blocked by furniture or dust-kittens, and since they heat up the objects & people in the room rather than first transferring heat to the air, which then needs to convect to distribute the heat, it's a lot more comfortable at lower room temperatures. It's OK to oversize them a bit, but not by more than 50% for the heat load of the room- you want it to feel like you are in front of a sunny window and not a broiler when they are on for extended warm-up periods.

See: http://www.heatinggreen.com/products/cove-heaters/

http://www.rosebudelectric.com/products/cove_heat/index.html

Radiant coves are a reasonable way to temperature balance the doored-off rooms when the house is being heated by only 1-2 mini-splits. It's fairly straightforward and inexpensive to use occupancy sensors to automatically turn them off when the room isn't in use, to guarantee most of the heat is being supplied by the heat pump, and only from the resistance heater when needed.

Thanks for the reply. The cove heater are double the price of baseboard. Have you seen the dimplex lpc series? That's what I'll use. They are proportionate so they don't work only on/off and they are much smaller than regular baseboard... and they are remotely controlled and programmed, so I can control the temperature and not have the children raise it back... Alexis

follow up question:

since my heat requirement for baseboard is low and the wall very well insulated, I suppose I don't need to put a lot of little baseboard and can have only 2-3 2500W basebaord per storey. If people in superinsulated house put only one or two mini split head and heat the whole house, I should be fine with +-5 large baseboard for the whole house?

thanks

I had not seen the Dimplex LPC series, but they look like a good product.

As with mini-splits, look carefully at the room-by-room heat loads, and consider whether the doors to the common areas will normally be closed, particularly on the overnight hours. You will probably want individual baseboards for bedrooms, but with the heat source located with reasonable convective paths to the more open spaces you won't necessarily need one in every room, especially rooms where the door will normally be left open.