Heating Plan in a Barn/Home

9 years ago

I have a medium size barn in Michigan. I plan to convert this barn into a single unit family residence. The walls will be CC foamed to an approx R21. The attic floor (that doesn't exist yet) will be approx R49. Main floor square footage is 2300 sq ft and ceiling height is 12 feet. Upstairs will have 4 bedrooms, 2 baths and a kids open space and be approx 1600 sq ft. with ceiling height of 9 feet. House is on propane. Plan at this point is for a 400 AMP service.

The barn currently has a slab concrete floor. Current plan is to add hydronic floor heat on top and then pour self leveling concrete before LVT'ing the floor to finish.

Question for you all is this: With an assumingly well designed pex tubing plan, will hydronic floor heat and the use of several ductless split system heat pump units suffice to keep the house cool in the summer and warm in the winter? Thats a big question--I know. Just looking for some opinions from across the fruited plane.

I want to avoid ducts if possible inside the home. But I also want to ensure efficiency and cost. I have a few HVAC firms working on this too, but you all usually provide excellent information. Thank you kindly!

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Comments (4)

ionized_gw
9 years ago
Ground source heat pumps (AKA geothermal which is incorrect IMHO) used to be a thing. They are probably not such a big thing anymore because of low gas prices. You, however, don't have natural gas due to a rural location. That is a problem that I am very familiar with since I come from that location. If you are going to be in the home for some time, it may pay to go that route but the front end investment is high.

You can heat and cool the space adequately with anything that you like as long as you match the output capacity to the building. I hope that you plan on a thermal break and insulation between the existing slab and the heat and what ever else you put above it.

Ground source is an excellent way to drive in-floor radiant heat. Low temp water is what is called for and that is what ground source excels at. Heat pumps can also provide chilled water to power small chillers in each room if you want to avoid ducts. That kind of thing is done commercially/industrially all the time and can be done in homes. Why do you want to avoid ducts? As long as you keep them indoors, and have balanced flow, they are not a problem.

Have you considered hiring a residential energy rater to help you out? They can do the calculations that help you determine if ground source is good and all the other decisions. Several models can be built and choices made. I really don't have a good head for your insulation numbers. If you construct tightly enough and insulate enough, it really does not matter how efficient or inefficient your heat or cool sources are since they will be little-used. You need some numbers to make those decisions. Local energy raters know what energy efficiency subsidies might still exist. Interview a hand-full and see what they can do for you.

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sktn77a
9 years ago
last modified: 9 years ago
Mini splits will cost an arm and a leg to cover 4000 sq ft. I know you say you don't want to run ductwork but you could build a chase into a wall to run it. It will be less expensive in the long run with a regular air to air heatpump split system.
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mike_home
9 years ago
The most important item for you new structure is to have someone do a load calculation. You are installing higher than typical insulation values so the rules of thumbs HVAC contractors like to use will not be accurate and result in an over sized system. If that happens you will be uncomfortable and waste energy. If a contractor tells you a load calculation is not necessary then look for another contractor.

My recommendation is two forced air ducted systems, one for each floor. If the funds are available then two-stage variable speed equipment would be a good choice.

The tax credit for ground source heat pumps is no longer available. Without the credit a ground source heat pump is not practical for most residential homes especially for one that is insulated as well as yours. It may make sense to install air sourced heat pumps and use the propane as the back up heat. You would have to run the numbers see which would be more economical to operate given the winters in Michigan.
ionized_gw
9 years ago
I think that Mike's seat of the pants view on the expense of ground source is probably correct. In a super insulated structure, there is not much pay-back potential in a super efficient heating or cooling source. In fact, with enough insulation, you can get to a point where just using resistance electrical heat might be competitive in a calculation that takes equipment life into account.

I wonder if with heat pumps, with high insulation levels, if heat strips or propane are necessary for comfort during defrost cycles. If heat loss is low enough, you won't notice the heat being of for the defrost time. Keep in mind that is what is happening with the most common mini splits.

Floor heat is oh so comfortable. Combining that with mini splits, or any kind of cooling is going to be a lot more expensive than having forced air cooling and heating in one system. If, in your area people are generally pretty happy with window units for a short and not brutally-hot summer season, a limited number of strategically-placed mini splits could handle your cooling quite nicely. It won't be central air, but you could be happy.