DIY Insulating
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N80
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Here is the followup. I priced fiberglass rolls and batting to do the whole job myself. Then I got an estimate for professional blown in in the attic and batting underneath and the price was almost identical. No brainer as far as I am concerned. I might could have saved some if I'd blown it in myself but probably not enough to make it worth doing in this heat.
Now, here is a follow-on problem. We had the central AC/heat installed. I think it is a '1 ton' unit. Maybe 2. I have no idea what that means. (Cabin is 3 rooms + small bath, about 1000 sq ft. total with cathedral ceiling in great room.) But, last week when it was hot (95) it did not get the temp below 80 until it got below 80 that night. It had run all day, non stop.
The AC guy said it was because we did not have insulation. He might be right and I'm getting the insulation in next week. But, the two window units we have work nearly as well and that's with no insulation too. There is cold air coming from the vents but it just won't do the job. I think either the unit is too small (it looks huge!) or something is wrong with it.
We'll give it a try with the insulation in but I'm doubtful. What do you guys think?
Now, here is a follow-on problem. We had the central AC/heat installed. I think it is a '1 ton' unit. Maybe 2. I have no idea what that means. (Cabin is 3 rooms + small bath, about 1000 sq ft. total with cathedral ceiling in great room.) But, last week when it was hot (95) it did not get the temp below 80 until it got below 80 that night. It had run all day, non stop.
The AC guy said it was because we did not have insulation. He might be right and I'm getting the insulation in next week. But, the two window units we have work nearly as well and that's with no insulation too. There is cold air coming from the vents but it just won't do the job. I think either the unit is too small (it looks huge!) or something is wrong with it.
We'll give it a try with the insulation in but I'm doubtful. What do you guys think?
IslandTractor
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I don't know exactly what a "ton" of A/C is but I recall it is about 20,000BTU or so. That's about the same as two big window units if I have my figure right. IMO a one ton unit in a 1000 sq ft cabin with poor/no insulation in the South then that unit is not likely to get you more than a 10-12 degree delta in indoor/outdoor temperature. Insulation should certainly help though, especially in the attic.
We have an old Victorian home about 3800sq ft with blown cellulose in the attic. Last week for several days it was in the mid 90s in Boston and our 4 ton A/C was running constantly starting mid morning to get the temp down to 78. Our A/C to sq ft ratio is about the same as yours but we have about two feet of attic insulation. The delta for us was about 15-16 degrees. Like your experience, it didn't get lower than 78 until the evening temperature dropped to the low 80s. We don't live in the south so purposely "undersized" our A/C a little to maximize dehumidification and knowing that we get less than a dozen 90 degree days a year. We also find a dehumidified 78 degrees to be quite comfortable.
We have an old Victorian home about 3800sq ft with blown cellulose in the attic. Last week for several days it was in the mid 90s in Boston and our 4 ton A/C was running constantly starting mid morning to get the temp down to 78. Our A/C to sq ft ratio is about the same as yours but we have about two feet of attic insulation. The delta for us was about 15-16 degrees. Like your experience, it didn't get lower than 78 until the evening temperature dropped to the low 80s. We don't live in the south so purposely "undersized" our A/C a little to maximize dehumidification and knowing that we get less than a dozen 90 degree days a year. We also find a dehumidified 78 degrees to be quite comfortable.
Redbug
Veteran Member
George,
You may want to have your AC unit checked out. It may be low on freon. It will run and run when low and never cool things down.
I'm not an AC man, but by putting a thermometer in one of your cold air vents you can read the air temperature coming out and see if it is too warm caused by low freon or something else.
Hopefully, one of the TBN folks, (that knows more than I), can tell us about what temperature the cold air from the unit should be at whatever the outside temp is when the unit is operating. That is, if it's 95 degrees outside and the AC unit is putting out 73 degrees of cold air into your house, (22 or so degree difference)...the unit itself is OK. I am curious to know myself...anyone know what the normal difference should be for a fairly efficient unit?
I think Island pointed out how to figure the correct tonnage. If you don't mind Island or George...can you elaborate a little more on the sizing since I am curious and don't know much about this, also.
You may want to have your AC unit checked out. It may be low on freon. It will run and run when low and never cool things down.
I'm not an AC man, but by putting a thermometer in one of your cold air vents you can read the air temperature coming out and see if it is too warm caused by low freon or something else.
Hopefully, one of the TBN folks, (that knows more than I), can tell us about what temperature the cold air from the unit should be at whatever the outside temp is when the unit is operating. That is, if it's 95 degrees outside and the AC unit is putting out 73 degrees of cold air into your house, (22 or so degree difference)...the unit itself is OK. I am curious to know myself...anyone know what the normal difference should be for a fairly efficient unit?
I think Island pointed out how to figure the correct tonnage. If you don't mind Island or George...can you elaborate a little more on the sizing since I am curious and don't know much about this, also.
IslandTractor
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Correction. One ton of A/C is only 12,000 BTU. That is the equivalent of only two small window units. Certainly would not expect that to keep a 1000sqft home without attic insulation cool in 90+ degree heat.
From Wikianswers:
Air conditioners are rated in three ways, by B.T.U.'s, Tons of Refrigeration, or by Horsepower. One Ton of Refrigeration removes the amount of heat needed to melt one ton of ice in 24 hours. One Ton of Refrigeration can remove 12,000 B.T.U.'s of heat in one hour. The B.T.U. is the amount of heat needed to raise 1 lb. of pure water 1 deg F.
From Wikianswers:
Air conditioners are rated in three ways, by B.T.U.'s, Tons of Refrigeration, or by Horsepower. One Ton of Refrigeration removes the amount of heat needed to melt one ton of ice in 24 hours. One Ton of Refrigeration can remove 12,000 B.T.U.'s of heat in one hour. The B.T.U. is the amount of heat needed to raise 1 lb. of pure water 1 deg F.
OP
N80
Super Member
Just checked, its a 2 ton unit. But a lot of good that will do me, we never get 2 tons of ice around here in the summer.
Anyway, we get insulation in next week. If the AC is still lame then they'll have to bring in a bigger unit. I don't need the dang thing when its 80 outside, I need it when its 95! And when its humid and 95 out I want to walk into a dry 75 when I've been working outdoors all day.
I'm also wondering if the logs have anything to do with it. I can't prove anything but watching the thermometer in the summer, the inside temp continues to climb for several hours after the outside temp has started falling. This leads me to believe that these logs hold a lot of heat, but this may be true in any structure for all I know.
Anyway, we get insulation in next week. If the AC is still lame then they'll have to bring in a bigger unit. I don't need the dang thing when its 80 outside, I need it when its 95! And when its humid and 95 out I want to walk into a dry 75 when I've been working outdoors all day.
I'm also wondering if the logs have anything to do with it. I can't prove anything but watching the thermometer in the summer, the inside temp continues to climb for several hours after the outside temp has started falling. This leads me to believe that these logs hold a lot of heat, but this may be true in any structure for all I know.
dave1949
Super Star Member
It's possible the sun is striking more directly on the side walls than the roof in late afternoon/early evening. The outside temp is going down, but you are getting more direct sun on the walls too. That heat can then be radiated into your interior space.
I have no experience with logs, there are claims that a log wall has a higher 'effective' R-value than it's rated R-value.
I was happy to hear you found a good solution on the insulation, that is one nasty job in hot weather.
Dave.