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Passive Solar Heaters: boxes, walls, attics

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  • #16
    Originally posted by Edmonton PRT View Post
    Maybe hook a duct from the top of your chimney to capture the waste heat and connect the other end to your furnace intake. A closed cycle is very efficient and keeps the carbon monoxide and carbon dioxide from getting out.


    no, don't do it.
    Problem solved: Just wear face masks with tubes to bring in breathable air from outside.

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    • #17
      Originally posted by nobleea View Post
      There's no way your attic, at any depth is going to be warmer than the current cold air location. Not to mention it's going to be drawing cold air from the attic space to keep the furnace supplied. Drawing your cold air intake from outside, even if painted black is also a lose lose proposition. On a sunny day (when you would benefit), the furnace isn't on that much. The cold dark, windy nights is when it's working full time and you'd lose so much.

      HRV is the answer. There are hundreds of people far smarter than us who have done all the testing in controlled experiments.
      I’m aftaid you are right. And that’s why we are still building “the same old, same old”. I’d guess that experiments have probably just proved that decent windows and insulation with the old mid efficiency furnaces make the most financial sense.
      (Payback on high efficiency furnace, chimney mods. etc are likely far, far out - another government mandated expense.)

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      • #18
        Originally posted by Edmonton PRT View Post
        If your attic is warmer, that is a bigger problem. You need more insulation R50-R60

        My attic is stuffed with insulation. Nonetheless the heat rises through the insulation and then, if it’s still above the ambient temperature, into the attic airspace. Therefore I was wondering if some of that heat loss could be cycled back into the house rather than escaping into the attic.
        Last edited by KC; 12-03-2019, 04:21 PM.

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        • #19
          Are HRVs Cost-Effective? - GreenBuildingAdvisor
          “Compared to a simple exhaust fan, a heat-recovery ventilator saves energy — but it probably won’t save enough to justify the high cost of the equipment”
          https://www.greenbuildingadvisor.com...cost-effective


          Broken Ventilation Equipment Goes Unnoticed for Years - GreenBuildingAdvisor

          https://www.greenbuildingadvisor.com...iced-for-years

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          • #20
            ^^If your attic temperature is above the indoor temperature of your home, your attic is either insufficiently ventilated, the attic insulation is not as good as you think it is, or both.

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            • #21
              Originally posted by KC View Post
              Are HRVs Cost-Effective? - GreenBuildingAdvisor
              “Compared to a simple exhaust fan, a heat-recovery ventilator saves energy — but it probably won’t save enough to justify the high cost of the equipment”
              https://www.greenbuildingadvisor.com...cost-effective


              Broken Ventilation Equipment Goes Unnoticed for Years - GreenBuildingAdvisor

              https://www.greenbuildingadvisor.com...iced-for-years
              This is probably true. For the fairly insignificant amount of outdoor air drawn into a new high efficiency furnace an HRV or air to air heat exchanger is probably not going to save all that much in energy costs.

              Forced air heating is by design a relatively inefficient way to heat a house. Hydronic heating is more efficient and allows for much more design flexibility. When we build our new house in BC I'll be designing a hydronic heating system with an outdoor air make-up to go into it.
              Over promise and under deliver. It’s the most Edmonton thing you can do.

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              • #22
                Originally posted by East McCauley View Post
                ^^If your attic temperature is above the indoor temperature of your home, your attic is either insufficiently ventilated, the attic insulation is not as good as you think it is, or both.
                No, in the winter the house is warmer than the attic airspace. (I would guess though that the temperature on the top surface of the insulation in the attic is above that of the general attic airspace but there’s probably a ton of factors at work there too.)

                At the time additional insulation was blown in, the depth of the old and new was about 18” (maybe more - I can’t recall as it’s been two decades). Soffits are perforated, small gable end vents and two Whirlybirds per level.
                Last edited by KC; 12-03-2019, 04:47 PM.

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                • #23
                  Okay. Wasn't sure what you meant by ambient temperature.

                  We added extra ventilation to our attic when we had our shingles replaced last summer. It reduced the ice damming problem we were having before at the bottom of the ridge line of the roof facing south and west.

                  I also had a contractor come out last fall to look at adding additional insulation to the attic floor on top of about a six inch layer of loose cellulose insulation that is over 30 years old. He recommended against putting new insulation on top saying loose cellulose that old has packed down and lost much of its insulating value. He was also concerned about the additional weight on our ceilings of not removing the old insulation first. But of course removing the old attic insulation before installing new increased the cost considerably so I delayed making a decision until this year.

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                  • #24
                    Originally posted by KC View Post
                    I’m aftaid you are right. And that’s why we are still building “the same old, same old”. I’d guess that experiments have probably just proved that decent windows and insulation with the old mid efficiency furnaces make the most financial sense.
                    (Payback on high efficiency furnace, chimney mods. etc are likely far, far out - another government mandated expense.)
                    Uh, we are not building "the same old, same old" in terms of new product. HRV/ERV's are pretty much a requirement in all new homes, along with all high efficiency gas fired appliances, higher insulation requirements, better windows etc. Every few years the government has been turning the dial up on that kind of thing in terms of better/tighter codes. As far as existing homes go, yes, it's often the case that upping furnace efficiency by only a few percentage points isn't going to yield an appreciable payback and you're better off reducing heat loss instead.

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