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Thread: Insulation questions

  1. #1
    Senior Member jp1's Avatar
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    Insulation questions

    When we bought our townhouse last fall we were concerned that it doesnít have central a/c despite the weather here being markedly warmer than in the city, where virtually no one has a/c. Ultimately we decided to get a portable a/c unit for my office since that room faces southwest and gets pretty warm in the afternoon. It cools off enough here at night that sleeping has been fine and itís usually several degrees below 70 inside in the morning just from opening windows and putting box fans in all 3 bedroom windows to bring in the cool air overnight. Then I close everything in the morning and it gets to the low 70ís downstairs and the high 70ís upstairs with no a/c. (For example yesterday it got up to 90 outside and 77 in the office by 5:00 when I stopped working, today itís only 82 outside and 73 in the office at 4:00, no a/c either day). We can live with that so weíll probably forgo the ongoing cost that a/c would cause, at least for now.

    But I would like to reduce the need for a/c in the office to just the hottest days, those that get over 95 really. Since this place was built in the 70ís the insulation is old and was undoubtedly mediocre to begin with. The problem is that the entire upstairs except for an attic space over the master closet and hall bath has the ceiling attached to the rafters of the roof. Even the attic area has the ceiling drywalled with only a small gap in a narrow section.

    My question is how difficult it will be to take out the old batt insulation and replace it with more effective insulation. Will an insulation contractor be able to pull out a relatively small part of the attic ceiling drywall and do the work, or will they need to pull out a lot of the ceiling. Also, similarly, how destructive is it to have insulation put in on the wall of the office and 3rd bedroom that faces the southwest.

    I like the idea of a onetime expense rather than using an energy hogging technology to stay comfortable but dread the mess/expense of the insulation people having to rip out drywall all over our upstairs. Especially after we spent money up front to have the awful popcorn ceilings removed and the entire upstairs repainted just nine months ago.

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    All the ceiling will have to be ripped out as more energy efficient would be spray in.
    Without actually doing that, you actually have no idea what is in there. It would be easier to cut a hole in the wall to see what is in the wall and patch it, then the ceiling.

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    Senior Member SteveinMN's Avatar
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    You might want to get a "blower test" energy audit for your place. They should run under a few hundred dollars and your local energy company may offer some kind of deal on one. That will identify where air is leaking. Insulation may help, but it may not be the fix. In our house (circa 1974) the insulation is adequate (by 1974 standards) but we have convection gaps through places like the attic hatchway and (the biggest problem for our house) the area between the tops of the walls and the ceilings. Current (Minnesota) code wraps that junction but our house doesn't have it. You might be better off spending money getting that sealed up than putting more insulation in the walls.
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    Whats the reasoning on insulation being the answer? I mean if the heat is caused by sun hitting a wall or window hard then that's a different problem right, and about shading that.

    Here it's hot, a brutally hot summer and I can think of 10 million reasons why that is so, but do little about any of them. There's the asphalt radiating heat where I only wish there were plants but I have to park somewhere too, but the black tar is brutal, there's the indoor water heater, and the stove, there's little attic to speak of ...
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    Senior Member jp1's Avatar
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    My assumption is that the biggest issue is heat beating down on the roof all day warming the ceiling that then radiates it into the upstairs rooms. But maybe Steve is right. We have one of those infrared thermometers so later this afternoon I will check to see if the ceiling is significantly warmer than the walls a foot or two down from the ceiling. Itís 84 right now amd a bright sunny day so if my theory is correct than the ceiling should be significantly warmer than the wall below it. If not then maybe Steve is correct that my issue is more one of air infiltration.

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    Senior Member jp1's Avatar
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    It appears that Steve is probably right. The ceiling of my office is 82 degrees. An interior wall a couple feet down is 80. At people level itís 78. Outside is 86. It doesnít appear that the heat is radiating down from the roof, at least not much of it.

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    Is your office window(s) double pane? If not, I’d start there. And I think PG&E is still offering rebates for making windows energy efficient.

    also, you mentioned a portable AC. Is it vented to the outside?
    Last edited by mschrisgo2; 7-24-21 at 8:16pm. Reason: Spelling, blasted autocorrect!

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    Senior Member jp1's Avatar
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    Yes, previous owner upgraded to modern double pane windows. And yes, the portable a/c vents outside and is even double ducted so that it doesnít cause outside air to get sucked in to replace the hot air that gets vented out. Mostly I havenít needed it. 78 by 5:00 is fine for me. I wear shorts and a t shirt. If I had to dress like I was going to an office it would be a different story.

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    If the basic science - that heat rises - is in play here, it may just be the windows radiating heat and shading may resolve it... maybe?
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    Senior Member jp1's Avatar
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    Quote Originally Posted by happystuff View Post
    If the basic science - that heat rises - is in play here, it may just be the windows radiating heat and shading may resolve it... maybe?
    I'm thinking this may be the way to go. It would definitely be easiest, and undoubtedly cheapest, to just install some sort of roll down shades, or a large awning, on the second floor wall of the SW side of the house. If it just reduced the heat gain by 3-4 degrees during the afternoon that would be enough.

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