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Thread: New house! Eternal heater w/ solar preheat?

  1. #31
    In the trades Dana's Avatar
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    Steve29 (if you're still looking here): I played around with the Taco tool a bit and if you kick the ventilation & infiltration numbers down to 0.1 or even 0.05 to account for moderately air tight construction and heat recovery ventilation (HRV) I think you'd get a bit closer to reality. Doing a quick model of my home with it against measured reality it's hitting ~20% above measured reality, even with 0.1ACH. Watch out for the cubic feet per square foot ventilation entry, as the tool will use the greater numbers in the calc. (You'll note that on the results page it looks like they're calculated 2.0 ACH, not 0.5.

  2. #32
    General Engineering Contractor ballvalve's Avatar
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    You want warm air on your FEET, not the top of your head.

  3. #33
    In the trades Dana's Avatar
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    Naw, you want warm SURFACES at your feet- the air temp at your hardly matters. Radiant floor is the top of the food chain from a wintertime comfort point of view.

    But radiant ceiling in a well-insulated building is the next-best thing and a close second at that. A radiant ceiling heats up the objects below, including the floor, (just not to temps that matter to bare feet.) Radiant ceiling never gives off that oppressive "under the heat lamp" feeling that even halogen down-lighting can, but the chairs/couches/tables/floors are all directly heated by the radiant ceiling- it's air contact with the warmed up stuff in the room that raises the air temp. In hot air/tepid-air systems the heat transfer is the other way around, from the warmer air to the cooler object. As a result it takes a few degrees higher air temp to hit similar comfort levels as radiant ceiling/floor or low-temp flat panel radiators (or even big clunky old-school higher temp radiators.)

    Low-temp low-speed air and constant room temps using ductless heat pumps isn't bad though- it's a noticeable comfort-improvement over ducted-air systems, but where you might be just-plain cozy at 68F with radiant you'd need to keep it at 70F or more to be as-cozy with low-temp low-speed air. But any kind of high-speed ducted stuff adds a wind chill and noise factor- to be avoided if you can.

  4. #34
    General Engineering Contractor ballvalve's Avatar
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    And take a look inside that 20 year old flex duct. Scary!

  5. #35
    In the trades Dana's Avatar
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    Reason number 177 why ductless is a better solution than ducted, when tepid-air it the heat transfer medium, eh? ;-)

    Flex duct is an abomination- I'm surprised it's even legal. It's only positive aspect is vibe-isolation when tying into a cheap noisy air handler.

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