Attic insulation

[Daox]

To go along with adding the soffit vents I'm looking at adding some insulation to the attic of the house. It currently has 6" of fiberglass insualtion which is supposidly around an R-19. The recommended R value for my area (Wisconsin) is R-49! So, I was thinking of blowing in some cellulose on top of the fiberglass to boost it up to R-49. However, I'm also wondering if it would be worthwhile to go a bit higher than R-49? Does anyone have any info that compares added insulation to energy savings?

[truckncycle]

I just spent about 30 minutes searching the net and didn't find much. The only actual cost benefit that I found was for the UK. A lot of other sites said to calculate it but didn't give any other information.

Nationwide Building Society - Home Energy Advice - Cost benefit guidelines

My wife and I blew 35 bags into our house -- about 10 into our interior walls (sound deadening) and 25 into our attic (extra six inches). In our area, the box stores will loan you a blower if you buy 20 bags. We divided the attic into grids so that there was a natural stopping point for hose repositioning. We used walkie talkies to communicate but couldn't use them very well through the respirators. We settled on keying the handset multiple times to tell my wife to shut off the machine. Break up the insulation as it is fed into the machine.

[truckncycle]

I just found a site that may have a calculator but it is a gov site so it may come up with the same 48 R-value.

Insulation Fact Sheet

[larryrose11]

Daox,
FIRST seal up your attic area: Put expanding foam along the top of wall headers, wire protrusions and such. The existing fiberglass can be your guide: It will be dirty wherever the is an air leak. I can not emphasize the sealing enough.
On attic insulation.
I would use cellulose over the top, not fiberglass. Testing shows that it just dosnt perform as rates in the cold! It looses 20% of its r value.
The fact sheet I have seen recommending R-49 from the enegystar website: Recommended Levels of Insulation : ENERGY STAR
is dated from 1997, and is based on Natural gas prices from then.
I would shoot for R-60
On Eaves: Do you hav an energy heel truss? If not, (like my house) then you should put the good stuff along the eves, the r6.5 / inch board. Reason is, that area is thin, and with celulose, you will be only able to get 3.5 inches or R3.5/inch = 12.25 at the eves.
I did this, and a boat load of sealing, and my heating (Nat gas) bill drop dramatically. They are now $50 in the winter here in Det, MI.

[Daox]

Thanks for the suggestions guys.

I was actually reading up on that site a little earlier today truckncycle.

Larryrose11, its great to hear your heating bill is that low! My goal is to keep utilities under $100/mo average.

I had planned on sealing up the attic, although I haven't thought as much about that yet. It sounds simple enough. Can you recommend any specific product to use as far as expanding foam? I know there is Great Stuff, but thats about all I know of. I definitly plan on using cellulose instead of fiberglass. Just the thought of installing blown in fiberglass makes me itchy.

I'm not sure what I have as far as trusses go. I can pretty much bet its no energy heel though. The house was built in 1886. I'll have to take a look and see what can be done. How far in did you go with the polyiso insulation?

[dremd]

I have blown Cellulose in my camp works very well, is affordable, easy to install, is flame retardant and most of all, I just like the stuff.

and a DreMD top Tip if your walls aren't insulated (most of mine arn't). You can cut a small hole (1" worked at camp) and blow cellulose in. I strategically drilled holes in places that would be covered with pictures, moulding, used some outlets, installed 2 blank outlet plates. All and all made the place much more comfortable (rarely ever have the A/C on over there).

[larryrose11]

Daox,
My goal was to have R-35 of cellulose at the transition between the cellulose and the polyurethane foam, so that is 10 in thick. How far back from the wall header depends on your roof pitch. Mine is pretty shalow, a 3:1 pitch. The final block design was shaped like a wedge with the nose cut off with 2 small 1/2 inch strips along the sloping face to create an air chanel. I squirted a heathy dose of Great Stuff Foam on the top of the exterior wall header when I installed it. It works great. NO icicles anywherte, and a thermal scan showed no cold spots. It was a pain to install, but I kinda overdo things when I never want to go back to a spot in the house. An easier solution is to contact a polyurethane spray foam installer and have they do your attic in the trouble spots, like wall headers, recessed lights, and the eves. It will be cheaper for a pro to install the spray foam than the DIY approach because of the HUGE markup for the DIY kits, like Tigerfoam. I went with a pro installer when I did my exterior remodel, because his quote came in under the DIY material cost

[larryrose11]

Here is a pic of our exterior remodel, or at least the insulation layers. On the front is the 2.5 lb per cubic foot, 3 inch thick polyurethane spray foam in the stud cavity, and on the side you can see the 1 inch foam decking that is covering the spray foam. Overkill perhaps, but there are health issues in the house with mildew, which drove this solution. The foam contractors also installed a plug of foam above the wall header at the eves, and filed the joust cavity in the basement where the house meets the foundation. There is a fresh or make up air inlet in the basement with a sealing air valve that opens on air pressure. The furnace gas solenoid also drives a relay, turning on a small (80 CFM) exhaust fan insuring fresh air in the house in the winter. My heating bill would be lower If I had a high efficiency furnace, but I don't. The furnace is original 1963 equipment and in good shape. High efficiency furnace without good insulation just efficiently wastes heat.

[Daox]

Sounds like a very nice setup. What is the R-value of your walls?

While searching today I found almost exactly what you had posted before:


BTW, do you recall how much a 1" thick polyiso sheet costs?

[larryrose11]

The r value of my wall is 28. I have 39 in my attic now, I will have R-60 this fall.

Sheet foam cost? I believe that they were about $12 per 4x8 sheet.

The diagram is similar to my house, but I have no soffit vent. I had an ventilated drip edge installed with the exterior remodel, which provides me the ventilation I need up there. The difference is that I went overboard, and where diagram has fiber insulation, I still have more board there. I love foam board.

[Binger]

Originally Posted by Daox

so let me see if I understand this. The polyiso stuff would be those big sheets of that foam that is usualy put on behind siding. This is then cut into strips and laid in the rafters back into the wedge were the floor and the roof meet?

then the celulosic foam goes in over the top?

It looks like there is an air flow area from the soffit, above the roof insulation and out into the attic?

I'm learning all the time so forgive me for this, I under stand the advantages of air flow in the atic...but what does this do better than filling the entire attic with cellulosic or pink batts?

[larryrose11]

Originally Posted by Binger

so let me see if I understand this. The polyiso stuff would be those big sheets of that foam that is usualy put on behind siding. This is then cut into strips and laid in the rafters back into the wedge were the floor and the roof meet?

Yes

Originally Posted by Binger

then the cellulose goes in over the top?

It can go over the top. In my case, this area was thin on insulation and the only way to get a decent R-value was to use pollyscio foam where they have fiber insulation in the diagram because, the pollyscio foam is R-7/inch, cellulose is half that @ R-3.5/inch. and fiberglass is R-2.3/inch. So, if your are space constrained. use the highest R-value available.

Originally Posted by Binger

It looks like there is an air flow area from the soffit, above the roof insulation and out into the attic?

yes, that is the air passage.

Originally Posted by Binger

I'm learning all the time so forgive me for this, I under stand the advantages of air flow in the atic...but what does this do better than filling the entire attic with cellulosic or pink batts?

As I mentioned, it is best to use this foam board where you are space constrained. In this tight area on the diagram, you only have 3 inches. So, what to you want there? (7*3)= R-21 or (3.5*3) = R-10.5?
R-21 right?
Once you tackle these tight areas, the rest is easy.

Also, do you yourself a favor and avoid the pink bats. they have formaldehyde in them (FEMA Trailer anyone?), they under perform cellulose, and they LOSE 20% of their R-value when the temp drops below 30 F. The stuff sucks.

Before you install the loose fill cellulose, make sure you seal up your attic, like I said earlier in this thread.
Larryrose11

[Daox]

Just to clarify, polyiso is not (I believe) the normal foam board you buy at your local home improvment store. The normal foam board is called polystyrene and is cheaper and isn't quite as good at R-4 per inch of thickness. Polyiso (full name is polyisocyanurate) is a little different and as mentioned is R-7 per inch of thickness.

Also, cellulose is not a foam. It is a mixture of mostly recycled paper.


I'll be getting into the house at the end of the month assuming no hang ups. I'll be sure to post any progress here.

[larryrose11]

Daox,
Polyiso foam is avalable at Home Depot. It goes under the commercial name Super TUFF-R

Did I make a typo and call cellulose a foam? Its power-like Grey fluff. Works great where space is no concern, but wear a mask when installing in an open area.

[Daox]

Binger mentioned something about putting cellulose foam over the top. I was just clarifying for him.

Good to know you can get polyiso at the local chain improvment store. I kinda figured you could, but wanted to note there are more than one type of foam board avaliable. I'll have to check it out for pricing next time I swing by.

[elhigh]

The polyiso will look different, have a different texture. In my experience it's usually kind of an off-amber color, very fine grain.

Don't forget to keep your cellulose away from light fixtures, unless they're rated OK for insulation contact. Make a quick-and-dirty box to drop over the tops of fixtures to keep the insulation 3" away.

[larryrose11]

Daox,
elhigh,
ON recessed lights:
These things look nice, but you couldn't ask for a worse thermal offender. Typically they are double wall, with venting at the top and bottom, so they have a built in air leak. When they are on, the light bulb gets hot (Even CFL will get warm) and heat up the inner can. This heat is transfered into the air between the metal cans, where it rises to the upper vent, where it escapes, and room air is takes its place. This is a thermodynamic air pump. It is throwing your energy (heating or cooling) into the attic. The solution is to make boxes out of drywall (which is a fire rated material) and then cover this with foam board insulation, sealed up with GreatStuff. Drop these boxes over the recessed lights from the attic side, and back fill the gaps with more GreatStuff. You now have a airtight, insulated box with an air gap between the lights and the box, and a 15 min fire-rating.

[lgtech]

Hi guys,

Great thread! Sealing the air leaks and insulating the attic is top on my to-do list - the car has to wait. I'll be sure to take pics and post. I used 1186 gal of heating oil last year here in NH.

On the Great Stuff, I read in Family Handyman magazine the Great Stuff is *not* fire rated and should not be used for service penetrations between floors. In some cases, it is against code to use it; check with your local building inspector to be sure. Use something that meets ASTM E-84 Specifications and classified as a fire-rated foam insulation.

Have fun!
LG

[RH77]

Great thread

To expand the topic a bit, my biggest problem is the summer heat...

Aside from the built-in air vent / soffit setup, would it be beneficial to install an exhaust fan and inlet? I recall seeing one years ago that was hooked to a thermostat.

Also, do any new homes have attic fans anymore?

Last item: when it's hot on the second floor, I usually run the bathroom fans to pull the hot air out and let the cooler air from the A/C sink (the top floor ducts run through the attic and exit through the ceiling). The fans have a decent CFM rating (forget the number at the moment). The exhaust essentially looks like a dryer hose sticking out of the attic space. Is there a benefit vs. cost to this practice?

The house design is a traditional rectangle-on-rectangle 2 story (no level splits).

RH77

[larryrose11]

Originally Posted by RH77

To expand the topic a bit, my biggest problem is the summer heat...

Aside from the built-in air vent / soffit setup, would it be beneficial to install an exhaust fan and inlet? I recall seeing one years ago that was hooked to a thermostat.

Yes, these can be bennifical at cooling the attic, but generally, where the heat is coming in (summer)is where the heat is leaving (Winter), so a good sealing job (See above posts) is always in order. Also pay attention to the attic hatch. Think of it like a door. It my house, it was just a piece of plywood. I reinforced it with 2*4, heavily insulated it (I love foam board.) and put EPDM foam strip on both surfaces, the hatch and the ledge it sits on when in place. It seals nice.

If you have ducts running through the attic area, they need to be well insulated and sealed at the beginning and end. PILE cellulose insulation on top of the ducts. Make walls out of cardboard to hold the loose fill in place. If the ducts are metal, then I know that there are leaks along the path. Where they join are obvious problems. You can find the leaks by turning on the furnace blower, and with a stick of incense and a flashlight shining on the smoke. If the smoke moves at all while you slowly move the incense stick along the surface of the duct, then you found a leak. Seal up the duct leaks with aluminum tape, NOT duct tape. AL tape rocks!

Aside,
I would seal up all the duct work in a house you have access to. You can use Mastic, (furnace caulk) or AL tape. Use the incense method to find the leaks. you will be surprised at how many leaks you find. doing this ensures that the heated/cooled air goes to its intended location. In general, 30-50% of air in a HVAC system is lost due to leaks.

Originally Posted by RH77

Also, do any new homes have attic fans anymore?

Some do, but they are not std.
Unless directed otherwise, new house ae built to code, which is the bare minimum, and no where near good.

Originally Posted by RH77

Last item: when it's hot on the second floor, I usually run the bathroom fans to pull the hot air out and let the cooler air from the A/C sink (the top floor ducts run through the attic and exit through the ceiling). The fans have a decent CFM rating (forget the number at the moment). The exhaust essentially looks like a dryer hose sticking out of the attic space. Is there a benefit vs. cost to this practice?

The house design is a traditional rectangle-on-rectangle 2 story (no level splits).
RH77

What I did when I lived in a bi-level, is to use a house or window fan at night on exhaust on the upper level with the lower windows open. If you use a window fan, make sure that the openings around the fan are covered up so the air doesn't just circulate. Cool of the house as much as posable while the outside is colder than the inside, then close up the windows in the morning. When A/C was needed, cover up the send and receive ducts on the lower floor. leave 1 return open in the basement, but no supply's open in the basement. That way, the returns are open upstairs, the air that needs the most cooling. The supply upstairs get all the flow, and the cold air flows down the stairs via gravity.

When I say cover up the supply and return ducts, the built in louvers are a joke. Use a ex-shopping bag, stuffed full with other ex-shopping bags, and shove this in the supply duct under the grate. If this is not an option, use the flexible magnet material, available at your local hardware store to cover up the ducts.

Larryrose11