Question about 'R' value for attic insulation.

I'm in Fort Worth, TX and when I look at an online chart for the 'R' value of insulation I would need for my attic, it tells me 49. (about

14" of cellulose. I think)

At the local DIY store they tell me that this is really overkill and that about 30 will do about all I need.

Since we will be doing the 'blowing in' ourselves, I would appreciate it if someone who has done this themselves, in this area, would care to give their opinion of what 'R' value I will need.

Thanks.

Lewis.

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Reply to
limeylew
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You'll want to look at this document:

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Specificaly, at tables in the 802.2 section.

Basically, if it's a wood framed structure. R-25 is required if you're putting bats between joists, and R-19 if you blow in continuous insulation.

Remember, that's just code, the bare minimum requirement. If you want to put in more, go for it, your house will be more energy efficient.

Took me about 3 minutes to find by googling "Ft. Worth building codes"

Reply to
Abe

Also, pay attention to vapor barrier at ceiling level, insulation of ducts above the insulation, & venting. T

Reply to
AAllc.architects

or install foam blown in place, R6 per inch

Reply to
hallerb

Need or want? Generally, the more the better, but there is some diminishing return. In your area, it is probably a better benefit for AC than for heating. What is the cost difference doing it the two different ways? $100? Then go for the most. $1000? then I'd go closer to the R30.

As the cost of energy goes up, the return for more insulation gets better. Your energy cost may be 20% to 50% higher in a couple of years so factor that into your decision.

Reply to
Edwin Pawlowski

There are local minimums. I consider them just that. More is always better, but there comes a time when it becomes un-economical to go higher. Few people go that high. More efficient systems will mean less payback from insulation, but as time goes on, you can bet the cost of energy is going nowhere but up so I would suggest erroring on the high side. Don't forget to add additional insulation for any ducts that are running up in that attic.

Reply to
Joseph Meehan

Your original post said you were blowing yourself. I hope you saw the reply about vapor barrier. I am near Chicago and our requirement is R

  1. Typically a 6" R-19 batt with vapor barrier (always facing the inside) then blow on about 6 inches to get a consistant blown R-11 after settling. The next big issue is the attic ventilation. Buy foam chutes at the local home store to prevent the insulation from contacting the sheathing near the edges. This allows air to travel from the soffit vent up to the high roof vents. Without proper vapor barrier and ventilation you don't gain from insulation, it causes more trouble.

Dave Scudamore Aroundtoit Handyman

Reply to
DavesTeam

the more you can afford to put into the space, the more comfortable the house will be. we have always added new insulation into every affordable wall and floor.

Reply to
buffalobill

Thanks.

I'm working on the soffit vents and baffels.

WOW! This stuff makes a yoga class look like a walk in the park. :-)

Lewis.

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Reply to
limeylew

We are adding on to our house, and when I talked to my inspector about vapor barrier, he downplayed the need for it, indicating that we could use a primer under our paint which would be rated as a vapor barrier. He said that as long it had a rating of 1 perm, it would be ok.

JK

Reply to
Big_Jake

If he made that remark related to the idea of removing existing insulation in order to add a vapor barrier, I would suggest that it might not be a bad idea. On the other hand if he is talking about skipping the install of a conventional vapor barrier during a conventional install, I would suggest ignoring almost anything he says.

Reply to
Joseph Meehan

I looked up Pa codes, and found something weird. Eventhough R49 was in the IRC, Pa said 30 was ok. I thought about it this way further, money into insulation or money into the utilitie company's pockets. Needless to say I invested in my home.

tom @

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Reply to
Just Joshin

I know they make a paint that is supposed to be a vapor barrier. I would want to hear it from the paint dealer that his product is a full and complete replacement for the attic vapor barrier, not just a supplement. I owned and operated a home inspection company in the early 90's. You would be amazed at how many houses had the insulation installed upside down. Obviously, the city code inspector passed them when it was built. This traps vapor (read water) in the fiberglass with no means to disperse. Molded drywall results. If the warm moist inside air contacts the colder atmospheric temperature of a properly vented attic, condensation occurs. I know you don't have varying temperature like we see in Chicago but if they specify that much insulation they must expect it to insulate the home interior envelope from some exterior temperature extreme. Better safe than sorry.

Dave Scudamore Aroundtoit Handyman

Reply to
DavesTeam

Codes on insulation are minimums never the optimal, nor do they reflect present utility costs or future increases, most are way outdated. Whatever you put in it will settle, cellulose will settle the most and deteriorate as its only paper. My fiberglass settled 15%, for cellulose Id figure double as a guess. If winter heating is minimal a vapor barrier may noy be as big an issue as it is up north, Put in what is optimal, your DIY store employees really dont know.

Reply to
Mark_Ransley

Since he will be signing off on my permit, ignoring him would be really bad. :-)

JK

Reply to
Big_Jake
:

The electric utility in Tucson AZ (where its hotter than FW) says to go with R 30 Above that is a waste of $$

Reply to
Rudy

R-49 is not practical in an attic that will be finished. R 30 seems to be standard in most places. If you can ft more and want to pay thats on youbut 30 will suit most people fine especially when combined with a radiant barrier like reflectix.

Reply to
bigjim

I pointed out that it seems that local codes only require R30. However I never saw anything about using any radiant barriers.

Just saying, I'm guessing, the cost of fuels will go up. Just a guess... and with global warming causing the potential for more snow now. Don't ask me, ask Gore why we had a threat of wet snow lately. Having more insulation in the attic space, where able, might be a good investment in your home.

Just what I did, not an R-expert. ;)

tom

Reply to
Just Joshin

fwfrog had written this in response to

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: Although this post is nearly 2 years old, I find I'm in the same boat, in the same part of town as the original author of this thread. Can anyone advise?

We have a house that's over 80 years old, most brick exterior, roughly

1000 sq. feet with an open attic. We have a gas furnace in the attic as well.

There's a very thin layer of cellulose in place - but it's so bare you can see the 2x4's sticking up all along the attic floor.

We have two companies that have bid to blow insulation in our attic (as they put it, the "white stuff" that looks like "snow").

Here are the bids: R-30 (12 inches) for $200 R-38 (17 inches) for $460

-or- R-49 (inches unknown) for $698

According to the Energy Star chart, we need R-30 at the minimum.

Would R-38 or R-49 be worth the extra cost? Or is this overkill?

Do you have to live in the house for a long time afterwards to see a return in your investment (based on monthly savings in your A/C or heating bill)?

I should also mention that we had a brand new A/C unit (with, I believe, a SEER rating of 14) installed not even 18 months ago.

Any tips would be appreciated! Thanks!

------------------------------------- Edw>> I'm in Fort Worth, TX and when I look at an online chart for the >> 'R'

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Reply to
fwfrog

White Stuff? what Crack, be specific.

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will help. R

30 is below Minimal. R 40 Is better. R 60 Is great but it will settle 15-20%. I did R 100 and it settled to R 80. Heat rises so insulate better than the Minimal codes require.
Reply to
ransley

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