Insulation question

[Older'n dirt]

It's been a long time coming but I finally have a building standing in my yard. Still waiting on delivery of the O/H door and the house wrap & siding but I guess that'll get here eventually.

My question is this; I'm planning to use R30 insulation in the attic but I also want to put a floor in the storage area. Should I continue with R30 across the entire span and compress it with the attic flooring or just use R30 on the outer areas and use R19 under the floor?

Maybe the attached drawing will help clarify my question. (Bldg width is 30'. Not exactly to scale.)

 

[bww_mnm]

I've always read compressed = bad. I'm guessing R19 done right is better than R30 compressed. With that said, i'm no expert.

Check out the attached: http://www.terrylove.com/forums/attachment.php?attachmentid=5858&d=1228078045

 

[bww_mnm]

here's one more comment from Owen's website:


Question: What is the R-value of R-30 compressed to 7-1/2"?
Tom writes from La Jolla, California: "I have 2x8 ceiling joists. Is it better to stuff R-30 batts into it or go with 6 1/4" R-19 batts and leave a 1 1/4" gap? What is the effective R value of compressed (to 7 1/2") R-30? Location is 2 miles from Ocean. Temperature very mild (40-95F)"
Answer: We do not recommend compressing Fiberglas insulation. R-30 in a 7 1/4" cavity yields R-25. I do not have a number for 7-1/2" but it should be close to what I reported in the second sentence.

Fiber glass insulation works on the principle of trapped air pockets. By compressing fiber glass insulation, you decrease the amount of air trapped in the material. It is better to buy the product that fits in the space.

If you are insulating under an asphalt roof deck, we recommend a minimum 1" gap between the roof deck and the insulation.

 

[Older'n dirt]

Fiber glass insulation works on the principle of trapped air pockets. By compressing fiber glass insulation, you decrease the amount of air trapped in the material. It is better to buy the product that fits in the space.

That's exactly what I expected but I guess I just needed to see it in writing.

Thanks for the reply.

 

[jklingel]

As I've said 1,000 times here, I'd leave the FG at the store and blow in cellulose. Way, way better insulation in an attic. See buildingscience.com. Nice shop; can I work on my loader in there, old buddy, old pal?

 

[taskins]

I had the spray foam applied in my new house/garage and I am very pleased with it. That may be an option for you as well.

 

[Chetter]

I rolled the R-30 into my attic of the garage and I put down some planks for storage in the center of the trusses and my insulation is compressed under those planks. I'm not saying it's the thing to do, but I was not going to use 2 different thicknesses of insulation when I did my attic. I have heavy mill plastic that I stapled to the trusses then layed down the insulation. Facing down to the garage over the plastic is 1"x4'x8' foam panels that are held in place with 1x2" furring strips and is going to be covered with FSK paper for fire protection as well as heat and light reflection in the garage this spring so the garage will stay warmer without heat running as much hopefully.

 

[csp]

See buildingscience.com.

Since you recommend this site so much, how about a specific link on whatever it is you are convinced of?

I've looked at that site at your recommendation once and really didn't know where to be looking. It's not exactly a user friendly site and the homepage is very broad and general.

 

[spongerich]

I've read great things about the reflective insulating films and mats too. I was thinking about adding some in my attic to supplement the 200 year old rock wool that's up there now.

I'm using that mylar coated "bubble wrap" stuff behind my cast iron radiators (no insulation in the walls for me) and it makes a very noticeable difference in the rooms where the radiators are on outside walls.

 

[keweenawbee]

Just got the March 2011 issue of Fine Homebuilding. One of it's primary articles is about insulation and it states that compressing fiberglass actually increases it's R value over same type insulation sized for that space. Who knew?

 

[Older'n dirt]

I may have that issue. ('Murphy Bed' on the cover?) I'll check it out tonite.

Whooda thunk? I guess everything changes with time. I remember when eggs weren't healthy for you, ..................... then they were, ............... haven't checked this week.

 

[Chetter]

I've read great things about the reflective insulating films and mats too. I was thinking about adding some in my attic to supplement the 200 year old rock wool that's up there now.

I'm using that mylar coated "bubble wrap" stuff behind my cast iron radiators (no insulation in the walls for me) and it makes a very noticeable difference in the rooms where the radiators are on outside walls.

I am always researching things to try and make something better, just today I had a home energy audit done on my home to find out where I stand and I passed with flying colors. Anyway, I am looking to make my unattached garage more energy efficient as well since I do heat it 24/7 during the winter months and the FSK paper looks like a really good product to use to finish off my ceiling in the garage. I might even be tempted to use it on my walls since my garage is a pole style building that I wrapped and then installed 2" foam panels inbetween the girders and then installed 1/2" osb over that to cover the walls and painted them white. The FSK paper can be used on walls and it might something to consider later if you don't mind looking at the foil although I believe they also make with a white color instead of the foil. Just google fsk paper to find out more about it.

 

[keweenawbee]

No the murphy bed is the last issue. I think they skip Feb. I never throw these away love them for reference. I am using r38 in the ceiling and r19 in the walls, both sealed off with foil-bubble-bubble-foil. I am then adding a 1x airspace for wiring and any gas, air or water plumbing backed with solid foam blocking wherever I have deep boxes or penetrations to the outside. As I am DIY all the way I couldn't afford the spray foam contractor route so I hope this pays off as it is labor intensive.

 

[Older'n dirt]

Aside from hoisting the trusses and the roof sheeting, mine is a DIY project as well. Quite the exercise installing a 9' x 12' O/H door alone.

 

[keweenawbee]

It is amazing how similar our garages are. Yours is 4' longer but same width. I used 6/12 storage trusses for the first 24' and 6/12-3/12 scissors for the 12 X 30 guest quarters (I'm the guest until I build a cabin if I live that long as I am old as dirt too) I installed four Velux skylights with metal roof flashing above the living area. I have room for a mid level sleeping loft back there above the bathrooms and I plan to insulate the front attic storage walls too so it will be tricky maintaining the heat loss up near the peak. I will probably have to go with some spray foam. I have 16" of block below 10' 2 x 6 stud walls. I must admit I did hire a crane and operator for a day, but my wife was the "******" and her brother & I stayed up on those top plates all day setting the trusses. My wife and I actually jacked the plywood sheathing up to the roof using a pair of those wall erection jacks in a unique arrangement where they rode some guide rails I built. My overhead doors are 10 X 10 with a walk door in between them. Yeah that was fun too but I did have a friend help me on that one (with experience)

 

[tmars]

Yours sounds similar to what I am planning. Mine will be a 30x40 with attic trusses for the first 25 feet then scissor trusses for the last 15 feet. Can you post some pictures? I hope to get started in April, I am in central Illinois...Thanks