Helpful? 0

Help! Choosing Heating System for New Construction Home

We are in the final stages of design for our new home. Total square footage ~1700 with full basement under 1000 square feet and crawl space under remaining. Trying to plan for energy efficiency. Double 2x4 walls with cellulose insulation, efficient double glazed windows. Some insulation under foundation. Manual J was completed with Total Heating required including ventilation air: 25,116 BTUh. Efficient wood stoves planned for supplemental heat. We have a wood lot as a resource, and I anticipate we'll use the wood heat nearly every night in the winter.

Quotes for heating systems seem so high! We are looking at hydronic radiant floor heat. Quotes for propane boiler or electric boiler with radiant floor heat are in the $20,000 ball park with annual operating costs at ~$3,000. Ground source geothermal at near $30,000 with annual operating costs of ~$1,200.

So, this seems crazy to me. A small well-insulated house should not require a $20-30,000 heating system plus wood stove costs. Where are we going wrong? Should we be giving up radiant floor heat? Should we be putting an additional $10-15,000 in insulation and reducing heating system to perhaps mini-split ductless? Direct vent propane units? We are in a rural area and do not have access to natural gas.

My dream was for a passive house. We now seem to be in an in-between land. Above average insulation,etc. , but not "tight" enough to reduce heating systems.

Thanks for help/advice. We are in Zone 5 northern michigan, so heating is the primary concern vs. cooling.

Asked by Molly Straebel
Posted Tue, 07/05/2011 - 00:55

Tags:

5 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.
1.
Helpful? 0

"Above average insulation,etc. , but not "tight" enough to reduce heating systems." What has tight got to do w/ insulation? Did you mean "thick enough" instead of "tight"? So you are heating 2700 sq, right? Radiant heat on both floors (basement and house)? How much foam will be under the slab (I assume) in the basement?

Answered by John Klingel
Posted Tue, 07/05/2011 - 03:21

2.
Helpful? 0

Molly,
You wrote, "My dream was for a passive house." Then why did you choose double-glazed windows instead of triple-glazed? Probably because of the cost. Now you know that you'll end up paying higher heating bills because of that decision.

The cost of installing a heating system is determined by getting three or more bids from local contractors.

If you want to know about other options, you can read Heating a Tight, Well-Insulated House. However, your design heat load may be too high for some of these options.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 07/05/2011 - 07:10

3.
Helpful? 0

Yes, John, we are heating 2700 square feet. R-10 foam board on basement walls; I believe R-5 under slab. Radiant hydronic under wood floors on first floor only, not in basement. Is 25,000 BTUs a high design heat load for this size home?

And my "tight" I did mean "thick." Our builder is using techniques to also make the home tight. We hope to reduce thermal bridging with the double 2x4 walls.

Answered by Molly Straebel
Posted Tue, 07/05/2011 - 08:20

4.
Helpful? 0

Molly,

Will you be using heat recovery ventilation? A well built double wall home in a cold climate will require about 1 Btu per square foot per heating degree day, including mechanical (heat recovery)ventilation. Your house (if built properly) of 2,700 sf @ 8,000 heating degree days will use 21,600,000 Btu's annually or about 235 gallons of propane.

Insulate the slab and foundation properly and drop the radiant heat, you will not need it. To spend 30k on geothermal is a mistake, there is no payback. You are going to supplement with wood so your main energy load will be for domestic hot water and electricity. I would consider a small, high efficiency forced air furnace, you may not need AC in N Michigan.

If you insist on in-floor radiant heat, that system will run about 15k, go with a high quality unit like Triangle Tube. This will also take care of your hot water at 90% plus efficiency.

Answered by Doug McEvers
Posted Tue, 07/05/2011 - 11:40
Edited Tue, 07/05/2011 - 11:41.

5.
Helpful? 0

This is probably far too complex to answer in this format but here are a couple of suggestions. There is a certified passivhaus architect in Michigan that you could at least get some advice from if you don't want to start over. There are also other good architects, designers and consultants that could advise you on how to further reduce your heating loads. As for insulation and tightness, I generally consider these as insulating R value and infilitration.. Infiltration generally being the one most people just estimate, and also the one easiet to get wrong. Again, a good consultant should be able to get you past that. Then there is the issue of cost. In simple terms, if you are going to finance the cost of the home, you can weigh the monthly energy bill against that of the loan. More money upfront, higher mortgage payments, but lower energy bills. You can get as financially complex as you want but it is place to start. Personally I would recommend the radiant in floor heat as it operates at a lower temperature and can therefore be done with many different types of heating. Given the unknown cost of any carbon based fuel, such as propane and even wood, along with all the other issues that go with it, I recommend as least planning for solar and wind which allow for direct heating, in the case of solar, as well as electrcity which can be used for heating, pumps, lighting, etc. Hope this gives you a few ideas. Good luck and for the best you can do. Houses should be long term investments planned for long term quality.

Answered by Corian Johnston
Posted Tue, 07/05/2011 - 12:02

Other Questions in GBA Pro help

Hot water re-circ line & vertical head loss

In GBA Pro help | Asked by Joe G | Sep 30, 14

Detail and Insulation Review

In PassivHaus | Asked by Eric Burhop | Jul 31, 13

Detail and Insulation Review

In Plans Review | Asked by Eric Burhop | Jul 31, 13

Windows for my Pretty Good House

In Green products and materials | Asked by Matt Mesa | Sep 29, 14

LED GU24 base bulbs

In Green products and materials | Asked by Kelly Proctor | Oct 1, 14
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!