Geothermal vs HVAC, insulation - Montreal

nster3August 14, 2014

Hey guys, sorry for the long post about to follow


Renovating, gutted the house. Best combo of insulation, distribution and heating / A/C for savings and comfort in the next 10-15years?

Currently renovating a 1956 split-level. Main floor is 1500 sq. ft. and livable basement area is 600-700 sq. ft. Everything is currently stripped out. There was no previous insulation and was running on an old oil system and was distributed with hot water radiators (6000$ for heating last year). The exterior of the house is a mix of brick and stone brick, in the interior there's a layer of plywood on all the exterior walls. Electricity cost in my area is ~0.09$USD/KWh all-in I think. We plan on staying here 10-15 years. We have ripped out all electrical and plumbing and will be starting from scratch

For insulation the plan is to shoot 3-3.5" closed-cell foam on all exterior walls (space is precious) and standard drywall. For the roof it would be 12" of cellulose and in the garage ceiling (under dining room/kitchen) will have 9-10" cellulose. Any point in shooting foam instead of cellulose?

For distribution system the plan is simply to install a duct system. I think it will be necessary for ventilation anyways and probably A/C, but is it worth it to put something else for heating? Hear lots of good things for radiation heating but that seems to come with a really high cost

For heating right now seemed to simply be an HVAC/electric system. Not sure what GreenSpeed is, is that something to consider?

So now we are considering geothermal, as we can afford it, assuming it benefits us in the long run. First off, does it bring the value of the house up? We had an evaluator come and he said a 2 ton system should be fine, though I was thinking 3, but perhaps 2 ton would save money and for the cold days the backup electrical system would take over, hence his 2 ton recommendation? We don't have much land (no backyard, only a roughly 50x20 , width goes up to 25-30 on the widest, so I'm guessing horizontal piping is properly out of the question? I believe our basement is fairly close to the water table, is that a good or bad thing for installing a geothermal loop?

Do you guys have have suggestions? We are trying to find the right balance of comfort and long-term savings. Heating/cooling costs for an electrical system is estimated around 1500-2000$/year versus what for geothermal? If you have any suggestions for companies in Montreal, please let me know!

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Greenspeed is a type of high end air source heat pump made by Carrier which is advertised at 20 SEER/13 HSPF which is considered very efficient.

There is also a Mitsubishi air source heat pump which is also advertised for cold climate heating.

Air source is not as efficient as a ground source heat pump but it can be a lot less cost as well. You can look up the info on the manufacturer's websites.

If you decide to invest in a ground source, just make sure that it is cost effective for your situation.

When I looked at the data for my home, the cost to go ground source was only starting to pay off in about 10 years. Unfortunately with the life cycle duration of the equipment, it didn't look like a good investment in my particular case.

    Bookmark   August 14, 2014 at 11:32AM
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Thanks for the reply!

how big was your home / how many tons did you need?

    Bookmark   August 14, 2014 at 12:12PM
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Do you have access to natural gas?

    Bookmark   August 14, 2014 at 12:32PM
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They are willing to bring in Natural Gas only if we DON'T have a heat pump, also installation wise it is a bit more than electric. Is it worth it? I was thinking with a 9 cent / KWh tax-in price at all times it may not be worth it? The advantage I see with natural gas is that we could have a gas fireplace

    Bookmark   August 14, 2014 at 2:51PM
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The gas rate versus electric rate will determine which will is cheaper to operate. The added benefit of gas is using it for domestic hot water and cooking which is usually much cheaper with gas.

In addition a heat pump has much more wear and tear than either a gas furnace or a AC condenser. It is something else to consider if you plan to live in the house 10 - 15 years.

    Bookmark   August 14, 2014 at 3:35PM
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Geez, how are they going to know that you'll have a heat pump or not?

Just throwing these thoughts out there, but other advantages of nat gas could be a CNG compressor for a vehicle and fuel for a serious back up genset.

    Bookmark   August 14, 2014 at 7:13PM
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âÂÂGeez, how are they going to know that you'll have a heat pump or not?âÂÂ

In Montreal, where the OP is located, the cost of the gas line installation and rebates for Energy Star gas appliances is predicated on anticipated gas usage and NOT having a HP installed nor the âÂÂDualâ electrical rate which is ~4.4â/kWh at temperatures above
-12ÃÂC/10.4ÃÂF (most of the year) and ~18.4â/kWh at temperatures below -12ÃÂC/10.4ÃÂF (a small portion of the year). The âÂÂregularâ non-dual rate for electricity is ~8â/kW year-round.

This dual energy rate makes electricity VERY competitive with gas at temperatures above -12ÃÂC/10.4ÃÂF and still competitive even below. A geothermal HP with a modest COP of 4 will cost just 1.08â/kW of heat DELIVERED into the house - that VERY hard to beat! The same kW of heat delivered into the house with a 98% efficiency gas furnace in our region will cost about 8.6â/kW of heat delivered into the house. Geothermal wins hands down at all temperatures above -12ÃÂC/10.4ÃÂF. However, the electrical rate jumps to ~18.4â/kW once the temperature drops below -12ÃÂC/10.4ÃÂF. ThatâÂÂs still only ~4.6â/kW of heat delivered into the house at the same COP-4 with geothermal, still not bad and still better than gas. The rest of the electrical consumption remains at the very high rate of ~18.4â/kW for temperatures below -12ÃÂC/10.4ÃÂF.

Keep in mind that with geothermal the backup gas comes on to assist the geothermal and they work in tandem till the T-stat is satisfied. That is usually for only a short period of time and then everything shuts off except the blower that is usually on low stage. Or the geothermal can be shut off all together below -12ÃÂC/10.4ÃÂF as the electrical utility expects and gas only is used for heating.

BTW: The gas company monitors gas consumption and they WILL know if you have a HP. You can have gas and a HP but donâÂÂt try to take advantage of the rebates or incentives! If you do take the incentives, then youâÂÂre âÂÂinâ for about 5-years of gas no HP.


    Bookmark   August 14, 2014 at 8:55PM
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This post was edited by nster on Fri, Aug 15, 14 at 14:47

    Bookmark   August 15, 2014 at 9:17AM
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Wow, Hydro-Quebec needs to send more of that inexpensive electricity South! Very interesting rate electricity rate structure and very interesting interaction with the gas rates, but kind of complicated for the average homeowner.

    Bookmark   August 15, 2014 at 12:20PM
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They are working on it ;) for now we have a surplus so they are doing a HUGE project for High capacity lines that go from Montreal to the border

    Bookmark   August 15, 2014 at 12:50PM
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