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Attic Insulation Part 1

November 17, 2011
Our heating bills last year were obnoxious! Our home is 1300 sqft and in January and February our heating bill alone was close to $350. It was $500 with the electricity added (with the house kept at 60F). This summer I began investigating what we could do to help save money this winter. Obviously, the windows are a culprit and we are dealing with that as we can. The attic and basement were the next two areas to check. My research showed that 40% of a home’s energy may be lost through the attic and basement walls. One quick trip up the attic stairs and you will see that our attic has absolutely no insulation at all. Zippo, zilch, zero! There is actually quite a nice breeze up there. You would think we had a window open. During the winter the breeze rattles the door at the bottom of the stairs which is especially scary during the middle of the night. It sounds like zombies in the attic are trying to break into the rest of the house! (I need to stop watching The Walking Dead right before bed). Brutus our pet Bullmastiff is a certified zombie attack dog,  and so when Geoff is out-of-town he sleeps in the hall so he can guard the attic door. I suppose once we insulate the attic and the door stops rattling the zombies will probably go away. Of course this has become our first priority.There are so many opinions on how to retro-fit insulation in an attic (none of them mention zombie mitigation):

  •  Some say to go the “hot roof” path – removing all vents and sealing the attic with closed cell spray foam that acts as a vapor barrier (applied directly to the sheathing in-between the rafters). Research shows this may void your shingle warranty and cause moisture issues and ice damming (when water freezing on your roof creating a sheet of ice that expands and pushing backwards up between the shingles causing leaks once the ice melts).
  • Some say to insulate the attic floor with loose fill like cellulose. You can’t use the space for storage or living if you choose this option. Also, the blown-in insulation has the lowest R value of batt and spray foam so you will have to use more. The blown-in insulation also settles reducing it efficacy.
  • Some say to insulate in-between the rafters with faced fiberglass batt insulation. If you choose this option you must make sure that the ceiling maintains airflow since you are not sealing off all the vents. The fiberglass can not be allowed to block the vents (gable, ridge or soffit) otherwise you will have major moisture issues and ice dams.
  • Some say to use rigid foam in place of the fiberglass bats (higher R value), making sure to maintain airflow.

There are quite a few variables here. We decided that because of cost (spray foam and rigid foam are $$$), the way our attic is built (only a ridge vent no soffit vents), and it’s intended purpose (finished space) we have decided…….drum roll……………to go with faced fiberglass insulation in-between the rafters!!!

attic before

We spent the better part of last Sunday installing the baffles to the sheathing. The baffles are made of flexible plastic easily cut with a utility knife and attached with medium-sized construction staples. They are also incredibly cheap – thank goodness since we needed over 100 of them.

Marrying a gymnast has its perks! Look at that balance 🙂 Geoff is precariously crouching above the open stairwell.

The baffles ran from the ridge vent (along the ridge of the ceiling) to the soffits. We don’t have soffit vents, but we may install them in the future so running the baffles the length of the ceiling will allow the optimum airflow if we do end up installing them. This Old House has a nice little blurb on how to install them.

SECURE THE aluminum vent to the plywood soffit with 1/2-in.-long screws spaced 12 to 14 in. apart.
This Old House Step 5 – installing soffit vents

The Old House Gods finally blessed us with some good fortune in the form of killer deals on supplies for this project. We were wandering the aisles of HD right around close hoping to find the elusive 54″ left hand drain cast iron tub for under $500 (they say unicorns are easier to spot). After an exhaustive online search and calls to manufacturers we were about the give up and leave when I happened by the insulation aisle, and to my disbelief, there was the R-38 faced attic insulation on sale for 75% off! Each roll of 42 sqft was only $10 dollars, marked down from $40.  I dropped everything and bought them out for every last roll. HD was switching out to a no-itch version of the same brand – our benefit! We never did find that tub and so we are going to have to go with a miniature 45″ tub – but that’s another post.

Fiberglass is nasty stuff. If it gets in your eyes or your lungs it will be there forever – you will NEVER get it out. If it gets on your skin you’re OK, itchy, but OK. As your skins sheds the fiberglass will come off.  I can hardly see at night and I really like my lungs so we both suited up like fiberglass Ninjas ready to wage war on the battle of heat loss. So far we have been losing but this winter I hope to gain some ground.
But seriously – wear gloves, goggles and a face mask. You should also tape your wrist and ankles so fiberglass doesn’t work its way up your sleeves and pants.

That’s right, I am wearing a floral tool belt and it kicks butt

Remember, the airflow is protected by the baffles which make a 1-2″ space in-between the sheathing the insulation. Also, make sure to buy insulation at the right thickness, if your rafters are 6″ deep don’t buy 12″ insulation. You would think packing all that insulation into the cavity would be better but it’s not. Insulation works by creating and trapping airspace and that is why it is fluffy and light not dense and heavy. If you pack it in and compress the batt then all the air is pushed out and the R value will actually go down. Think of a down blanket or a sleeping bag, both trap air in between the fibers/feathers to keep you much warmer that a tightly knit wool blanket.

While laying on our backs with our heads by the soffits stapling the batts to the rafters, Geoff aptly pointed out the source of the soft breeze. Finger sized spaces running the length of the chimney with daylight and wind streaming through. My reaction was !!???%@$#%@ How on earth is Geoff the first person since 1932 to notice that the attic was completely open to the outside??? No wonder our attic was like a spooky haunted house until about a month ago when we went up there with 3 bug bombs and a shop vac. It looked like we had spread that fake Halloween spider web stuff all over our stairs and ceiling – except it was real! The spiders were just running up the chimney and hopping through the gaps right into the warm attic all winter long.  I mean, it really was a place zombies would hang out.

We filled the gap with what else – spray foam. I will say it again – it really is “great stuff”.  Geoff pointed out at dinner that evening in a million years long after humanity has ended and cockroaches rule the world all that will be left of modern construction is spray foam and linoleum tile.

Websites/ Documents worth reading on this subject:

Insulating your old home

Homeowners Guide to Insulating

6 Comments leave one →
  1. November 29, 2011 6:52 PM

    Bats are cute, like little black mice with wings. Not so cute in the attic though! You should definitly check into venting down the road, it will extend the life of your roof. Thanks for posting!

  2. November 17, 2011 2:26 PM

    Great post! Our attic space isn't set up to be useable space (no stairs, just a hole in the ceiling of the second floor for access), so the PO just put in blown in cellulose insulation. We also have NO vents in the roof – soffit, gable, or ridge. Oi vey. We'll get to that one day. We have a little colony of bats who live up there, no zombies. Maybe bats protect against zombies?!


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