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insulate ductwork? move ducts?

Posted by peonyfan (My Page) on
Thu, Sep 1, 11 at 21:09

I am having trouble deciding which expert to believe. One HVAC company and also an energy auditor recommend we insulate our ductwork (will cost $2300 with first one, energy auditor bundled job with others). The second company says it is already insulated on the inside of the duct, and although it does not have a stated R value, further insulation is not worth it.

Also the first company also recommends we move our ducts to the perimeter and replace the 4-way blower with a 2-way ($200/duct capped at $2400). The second says that it will not be worth the money to do that. The nice thing is the bid from the first company has itemized everything and letting us basically go as "basic" or "luxury" as we want, so we can go with them and not move ducts. The guy from the first company was wondering if we would be ok with our AC being out of commission for a day during installation, and I told him that we have our AC set at 81 and our heat set at 62 so we would likely be just fine, but I feel like some of the options he's giving us are for people who are only comfy at 75.

Some background info that might help. We are converting our ranch house in metro DC from electric baseboard to gas heat (planning to keep a few baseboard units for zone heat or to supplement in the basement, which has few ducts). Because we have a finished basement, it would be very expensive to put the furnace in the basement and add new ductwork. At the recommendation of several HVAC companies, we are planning to put the furnace in the attic and use the AC ductwork for heat.

There is not much room in the attic, so the first company says we have to move ducts now, as there will not be access later. I have to clarify with second company.

Both of these companies come highly recommended in various consumer publications. The first one has a reputation of being good but expensive. I tried to get bids from other highly recommended companies, but they felt like the job was too big for their very small company, and I think another was so overwhelmed by explaining the various ways the job could be done that he didn't follow up with a bid. Another highly recommended company gave a hand-written, not detailed bid and and was difficult to communicate with. Another company said I would not be comfortable with a furnace in the attic and did not recommend I heat my house that way and gave me a bid for baseboard hydronic heat (expensive!!). I also want a company geographically near us because I feel like you get faster service and better prices that way. So I believe these two companies are my best options.

Thanks for any advice.


Follow-Up Postings:

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RE: insulate ductwork? move ducts?

good luck


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RE: insulate ductwork? move ducts?

Aren't heat pumps popular in the mid-Atlantic region? How about heat pump mini-splits and use the electric baseboard as back-up


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RE: insulate ductwork? move ducts?

I think it is a little cold for heat pumps here. In multifamily homes that share walls, I think they are fine, but we have many, many days below freezing.


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RE: insulate ductwork? move ducts?

"I think" is not good enough unless you like to part with your money. When I have been walking around the Maryland area, not far from you, I see a lot of heat pumps. The low temp performance is steadily improving so don't depend anecdotal reports from people with units that are a few years old.

The number of outside walls has nothing to do with the physics of heat pump low-temperature performance, but everything to do with heat gain and loss calculations. More outside walls = more capacity, not different type of equipment.

The US DOE has work sheets to help you calculate the relative costs of operating gas heat vs. heat pumps with your current utility rates (as well as cooling costs with different equipment efficiency).


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RE: insulate ductwork? move ducts?

"The low temp performance is steadily improving so don't depend anecdotal reports from people with units that are a few years old. "

And you can always back up with another heat source, like gas if it is available.

There is only so much that can be done to improve HP performance though.

When the outside unit falls below 32 F frost forms, requiring defrost cycles to clear.
During the defrost cycle the unit is switched to AC and the backup heat used to avoid blowing cold air in the house.

No matter what you try and do, if the outside gets below 32 F you have a problem.


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