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House not cool enough - what improvements do I make first?

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  #1  
Old 08-26-06, 02:26 PM
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Question House not cool enough - what improvements do I make first?

I posted this on the A/C forum 2 days ago, but I am thinking this forum might be more appropriate.

Our AC can't keep up in hot muggy summer afternoons but I am not sure what to do first to improve situation. Please let me know what you think will give me biggest bang for my DIY buck without being too complicated.

Lots of great ideas on this forum - Thanks to you folks, I have already placed a 1 1/2" foam board above our pull-down attic stairs, put in outdoor solar shade on large dining room window, and put the foam insulation around outside wall outlets. But I've got a headache from looking at so many options: radiant barrier and/or add roll insulation in attic, insulate metal ducting that is accessable in basement, seal air gaps between attic & ceiling, buy cellular shades for windows that get the most sun, powered gable vent...

House built 1960, 1250 sq ft main floor over 1250 sq ft basement in Central Virginia - humid summers, about 3-4 snows a year. No insulation in walls or basement, but drop tile ceiling in the half that is partially above grade. All windows were replaced with double pane before we moved in. Attic with gable vents and approx 4" original insulation. Metal ducting, with all vents/returns at bottom of floor. AC in basements which also has several vents/returns & outdoor unit in full sun most of day.

Unfortunately, I didn't find this forum until we replaced 40 yr old unit (which kept us cool to 76 degrees last year) with new 13 SEER Bryant 2 stage central AC/gas furnace. (it looks like same size or larger than previous old unit). Now the hall thermostat reads 79 by mid afternoon. Techs have been out several times and unit is "functioning properly" and "it isn't unusual for a/c to cool only 15 - 20 degrees less than outside temp".

Sorry for the long post, but i wanted to provide enough info.

Thanks
 
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  #2  
Old 08-26-06, 03:45 PM
Ed Imeduc's Avatar
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Wink

The first I see is ===
4" original insulation. That like a R13 in all .Anything to day has a R30 or better thats like 12" to 15" of insulation. What you can do now is cut blocks of R19 insulation and put them up in the joist on the sill plate all around the home. help for AC and heat

"functioning properly" and "it isn't unusual for a/c to cool only 15 - 20 degrees less than outside temp".
Thats what most paper work will say are call for. Now if the unit is right you should have a 16o to 20o temp drop over the coil at the coil.

ED
 
  #3  
Old 08-26-06, 05:19 PM
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Hot help

Venting the soffits and roof ridge will also help. Make sure soffit venting is not clogged with attic insulation. Gable vents are OK, but not sufficient.
 
  #4  
Old 08-26-06, 07:07 PM
Join Date: Mar 2005
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House not cool enough - what improvements do I make first?

You definitely more insulation in the attic. Add 6" to 12" of blown in cellulose (more in western/northern VA) and make sure you have/keep good soffet ventilation. Do not use batts.

In the basement, as much as I think fiberglass is usually not the best insulation, cut pieces of R19 and stuff them between the joists to insulate the rim joist.

Forget about the rigid foam unless you have the time and patience to cut them perfectly or foam the gaps. If they do not fit well they just become baffles.

Do NOT insulate the floor between the basement and the first floor. Insulation will deprive you of using the cool "heat sink" represented by the natural soil temperatures in the summer.

Dick
 
  #5  
Old 08-27-06, 06:06 AM
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re insulating around rim joist

When y'all say "insulate around rim joist", are you talking about in basement? I am not sure of difference between rim joist and sill plate (if it matters) So would I put fiberglass insulation in the space between the top of the basement concrete block wall and the first floor? I can see outside light - appears to be underneath the front stoop so should I use caulk to first seal the edges (since insulation shouldn't get wet)?

Also, what's the easiest way to cut fiberglass insulation? I will wear protective gear, but still... Is it easier and cheaper to use rolls to cut up or batts?

Re insulating attic - Rolling out R-19 at 90 degrees to existing insulation is the plan. It shouldn't be too difficult because I don't have any soffitt vents to worry about, and no can lights. But should I do something about ventilation first? I did put a box fan up in the attic for a few days (top half was against gable vent blowing outward on the hot side), but the difference attic & indoor temps was just 2-3 degrees.

Also, any value in installing radiant barrier?

I am new to this "insulating thing", since our previous house in the desert had a covering of thick white foam and no attic.
Thanks.
 
  #6  
Old 08-28-06, 06:49 AM
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Cutting Insulation

When cutting insulation, I use a framing square and a utility knife.
Press the framing square down firmly on the insulation and cut along the edge of the framing square with a utility knife. You will need a board underneath to avoid damage to floor or whatever work surface you are using.
 
  #7  
Old 08-28-06, 11:00 AM
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While I agree that you need more insulation I think you are looking the wrong way! If the old unit kept the house cool and dry the new one should to if it is sized wright and installed wright.
 
  #8  
Old 08-31-06, 10:53 AM
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Airman.1994 - I think you are right, but I am not sure how to proceed. What recourse do we have? I was thinking of calling the salesperson who did the estimate - he had some knowledge of system requirements, but the topic of air load calculations never came up.

Plus to add insult to injury, we just got our electric bill and our August 2006 bill showed a bit more usage than last year.

Anyway, what do you think? Thanks in advance.
 
  #9  
Old 08-31-06, 02:00 PM
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You can check and see . What the temp drop is over the coil at the coil . you should have a 16o to 20o drop over the coil there. If the unit is working right.

ED
 
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