Rim Joist Insulation

[Ashful]

I know one co-worker who did it in his 1971'ish house, and swears it made an enormous difference, but have no first-hand experience from which I can speak about rim joist insulation. I imagine it would have to make a very big difference in how cold your floors feel, on the first floor.

 

[semipro]

I've called around and most prices to have a contractor do the spray foam seems to be around 700-800 give or take a little. That definitely seems reasonable.

The one thing I'd like to ask those of you who've had your rim joist insulated is what was the difference? Did you find that your energy costs dropped? Did the house feel warmer?

Sorry, no good metrics to go by other than it felt warmer.

 

[drewmo]

OP - Does NH offer any rebates on such work? Might make the pros doing it look a little more appealing. I believe Maine, through Efficiency Maine, offers $600 back on rim joist air sealing.

 

[woodgeek]

Dana, based on other airsealing I have done, I would attest that beyond energy savings, there is noise, pest, dust and allergen reduction, reduction in summer humidity and increase in winter humidity. Before I couldn't get the winter humidity up, now keeping it at 30% or so keeps us all a lot healthier. Many previously creaky floors now don't creak (caused by swings in outdoor humidity). Overall, great effects, like getting a new house.

Cons: some rooms might get less comfortable, requiring you to rebalance your HVAC system.

 

[Ehouse]

Something you might try, (I have not done it), set your table saw to 45* and bevel the ends of the pieces of foam. Cut them slightly oversize longways and make them tight as you dare top to bottom then friction fit them in. If you have fairly uniform spaces, you can rip them all in advance and the bevel will give you some leeway side to side. The friction fit will allow you to also place some loose insulation in the bay first to increase R value and bring the work out toward you for easier caulking top and bottom. That's my theory and I'm stickin' to it.

 

[Ashful]

I can't imagine table-sawing foam board. Must be almost as messy as getting tarred and feathered. If I can't knife it with a utility knife, I hot-knife it with a resistance wire on a bow saw frame.

 

[Ehouse]

I can't imagine table-sawing foam board. Must be almost as messy as getting tarred and feathered. If I can't knife it with a utility knife, I hot-knife it with a resistance wire on a bow saw frame.

A small panel saw works well too. You could set up a stationary hot wire and run your bevels on that.

 

[velvetfoot]

I cut a lot of foam boards on a table saw: it's not so bad.

 

[TradEddie]

I cut a lot of foam boards on a table saw: it's not so bad.

Me too, not nearly as bad as I expected.

For my rim joists I started with regular latex caulk, sealing the joints as best I could, often smearing caulk onto a gloved hand reaching far into inaccessible bays, then I put foam board or XPS cut slightly small or friction fit. On a cold night I went around with the IR thermometer and any bays that were still noticeably colder or showed a draft with an incense stick got another bead of caulk around the foam board. I then added Roxul on top in case anyone in the future would say it wasn't up to code. It took many, many hours but I'm very pleased with the results, and surely less than $200 in materials.

TE

 

[peakbagger]

Check into this program http://nhsaves.com/residential/retrofit.html They will figure out the best payback items and pay for the half the cost up to $4000. I got a lot of work done including rim joists. The utility also audits the work so the contractors have an incentive to make sure the work is done right.

 

[DamienBricka]

Dana B. When I bought my house 13 years ago I had no insulation in the wall and a R19 in the ceiling. I needed to open up the walls to redo the wiring. I debated a long time between Icynene (foam) and fireglass batt. I decided to go with Icynene. I went from paying $225 a month on the gas budget plan to nothing. I went all electric since the furnace was shot. I pay around $75 a month on budget with electricity. I remember the day the insulation was sprayed on it was 123/23/2002. That morning I was freezing with a 100,000BTU furnace to being to warm that first night. I am now a strong believer of sprayed foam and yes it will pay back in no time. My experience.

Damien

 

[EJL923]

I think rim joists is my next project. I just used tight fitting foam boards in my basement window bays. They are single pane swing open, which are very leaky and cold. Last year i placed fiberglass bats in the window which helped a bunch. This year i used foam boards with removable caulk so i can take it out in summer. Point, dont forget to check the health of those leaky windows too.

 

[Ashful]

You insulated inside the windows? If you're not providing a good vapor barrier, you're going to have lots of condensation on that cold glass. Are the window frames wood or metal, and are you concerned about the paint / rust / rot?

 

[EJL923]

We shall see if there is any condensation, i don't think there will be. I have seen people do this a lot. There is nothing that will be damaged if it gets wet, and i can monitor from the outside throughout the season. Both the window and the foam board is sealed from air leaks.

 

[Ashful]

If it's air sealed, then no problem. The rule of thumb is you need the outer vapor barrier (in this case, the original window) to be more leaky than your inner barrier (your foam and sealing), to avoid condensation. Reverse this, and someone's getting wet.

 

[DBNH22]

I have shceduled a day to have the rim joists spray foamed. I'm getting the 2lb closed cell sprayed on 3-4 inches thick for $860. As long as everything goes well it should be a good deal. Date is decmeber 12th. I'll let you guys know how it goes.

 

[DamienBricka]

Dana. What is the total length of the rim joist? And are they 10 or 12 inches high? When I did my house 10 years ago I paid $3 a square foot 3 thick.

 

[DBNH22]

Dana. What is the total length of the rim joist? And are they 10 or 12 inches high? When I did my house 10 years ago I paid $3 a square foot 3 thick.

I don't know what the measurments are but i've started pulling back some of the fiberglass batts that were stuffed in the joists in the basement and I can feel cold air coming in. The floor above the basement has been very cold the past few days. I have one of those picture windows that extends out over the foundation over bare ground. I looked underneath it in the basement and there's a pretty significant cold draft rushing in. The sorry R19 batt is no match for mother nature in this little area. The batt has become pure blaxck due to the air passing through it. I'm chomping at the bit to have the job done. Im hoping it will make a huge difference. Did you notice a big difference when you had your's done Damien?

I've also noticed lots of mouse droppings. I'm hoping that the spray foam pretty mcuh seals up all their acceess holes.

 

[DamienBricka]

Hi Dana,
On December 23, 2002. I had the whole house sprayed with Icynene foam (If I had to redo it again I would use a dense foam). That day it was done it was very cold outside. I went from seeing my breath to being to warm. The 100,000BTU gas furnace that had to be replace was removed as well as all the duck work. I could not find a gas heater small enough for the house. So I went all electric. My electrical company had an energy audit done on the house and the door blower test showed that the house was very tight.
So yes you will see a difference.
Damien

 

[DBNH22]

What is Icynene? I'm getting the 2lb closed cell foam. I'v been reading about the stack effect and how an uninsulated rim joist casues cold air to enter the basement and hot air to leave via the attic. I'm hoping that when the rim joist is sprayed I will have much warmer first level floors, the temp throughout the whole house will be more uniform and stable, and that my energy costs will be significantly reduced.

I'm debating whether to add more fiberglass batts to my attic (currently have r30 which is most likely performing like R20) or rip the batts out and start from scratch with cellulose blown in to R50. That's going to be a costly undertaking which would be next year at the earliest.

 

[DamienBricka]

Icynene is an open cell foam. I would not recommend it. Closed cell foam is much better. Attic blown cellulose would be my choice for your situation.
I am working on the drawings of my next home. For that one I will be using SIP panels. That is several years down the line.
No cold air coming thru the joist will make a big difference.
Damien

 

[semipro]

What is Icynene? .... I'v been reading about the stack effect and how an uninsulated rim joist casues cold air to enter the basement and hot air to leave via the attic. I'm hoping that when the rim joist is sprayed I will have much warmer first level floors, the temp throughout the whole house will be more uniform and stable, and that my energy costs will be significantly reduced.

I'm debating whether to add more fiberglass batts to my attic (currently have r30 which is most likely performing like R20) or rip the batts out and start from scratch with cellulose blown in to R50...

There have been some good posts here about sealing up the attic. Adding more fiberglass won't gain you much unless you seal the attic floor where wiring, plumbing, chimneys, etc. enter. In general, thermal insulation is not very effective unless you minimize airflow through it.

Edit: also, I can't see any reason you can't blow cellulose over the existing fiberglass. However, you'll likely need to pull up the what's there to install proper air sealing materials.

 

[DBNH22]

There have been some good posts here about sealing up the attic. Adding more fiberglass won't gain you much unless you seal the attic floor where wiring, plumbing, chimneys, etc. enter. In general, thermal insulation is not very effective unless you minimize airflow through it.

Edit: also, I can't see any reason you can't blow cellulose over the existing fiberglass. However, you'll likely need to pull up the what's there to install proper air sealing materials.

I've already air sealed the attic. This spring I pulled up the batts, air sealed with some cans of Great Stuff, and replaced the batts. Before I do anything in the attic with insulation I actually need to replace the baffles for the roof insulation. The ones there now are cheapos and some of them are missing. I need to get the kind that fold down into the joists so that they create a barrier between the soffit/ventilation space and the insulation.

 

[Ashful]

Mice chew right thru spray foam, and ants love the stuff, treating it like a giant ant colony. Make sure you have your rodent and insect issues fixed BEFORE using spray foam, or you'll regret the day the stuff was invented.

 

[woodgeek]

I've already air sealed the attic. This spring I pulled up the batts, air sealed with some cans of Great Stuff, and replaced the batts. Before I do anything in the attic with insulation I actually need to replace the baffles for the roof insulation. The ones there now are cheapos and some of them are missing. I need to get the kind that fold down into the joists so that they create a barrier between the soffit/ventilation space and the insulation.

I airsealed my attic in 2009. And then in 2010 I did it again. In 2011 and 2012 I found still more I missed. Then this summer I had some pros come in to finish the parts I couldn't reach. I **think** its done now.

A quick test to know if you are done....if is 20°F outside, is it below freezing in the attic?? Or not?

And most folks will jsut blow cellulose over batts...too expensive to rip out the old stuff, and then pay for extra cellulose.