Adding Extra Attic Insulation - Is it worth it?

wanttolearn

Here's a question for you insulation experts:

one of my bedrooms is built over the garage. this room is the coldest room in the house, and has a far greater heat loss than other parts of the house.

i have checked, and the room is fully insulated (i.e. floors, walls, and ceiling are insulated with batt insulation). the only area where i could possibly ADD insulation would be in the attic above the room. currently i would estimate that there is R-22 insulation in the ceiling of the room, and i could fairly easily access the attic and increase that to R-50 or R-60.

my question is: in practical terms, is that going to make any real difference? given that the walls and floor of the room are going to continue to have the same heat loss, will adding insulation to the ceiling have any noticable effect, when there is already R-22 insulation present today?

any thoughts would be greatly appreciated.

SWEI

Run a heat loss on the room and try changing the ceiling R-value. You probably won't see a lot of benefit past R-40, but as long as it's cheap and easy, no reason not to.

Does the room have insulated window coverings? That can often make a real improvement, especially at night.

JUGHNE

Can you actually see what is insulating the floor? Those bed rooms always get the short end of everything. Ductwork in the garage. Maybe only one run to that room. It might have 3 outside walls. Maybe no return air ducting.

wanttolearn

the floor has fiberglass batt insulation. i see if in the garage ceiling. and yes, there are 3 outside walls to this roof, so i am not sure what difference it will make to add insulation to the ceiling.

JUGHNE

Is there sheetrock on the garage ceiling?

wanttolearn

yes

JUGHNE

If the SR is not fully taped and sealed like the rest of your house then there could be a lot of air infiltration into that insulation for the floor. The fact that you can see the insulation somewhere indicates there may be openings. Insulation only works well if the air it is holding in place cannot move or experience air exchanges. FWIW

Larry Weingarten

Hello: Following up on what JUGHNE said, I'd look at using a blower door to find and then fix air leaks. Even good insulation cannot work well with a leaky structure. My thinking on insulation is to do more. What will energy cost in twenty years? May as well insulate so it works then too!

Yours, Larry

GW

These rooms have 5 cold sides, is it on its own zone?

Here's the bad news, you have entry level insulation. Your floors are being wind washed....I bet the floor in that room is much colder than any other floor in the house.

Your knew walls, is the insulation exposed opposite the sheet rock? 50% r valve penalty.

Any canned light fixtures? They can act as sieves. They must IC and air tight.

I could blab on a bit more. High performance means spray foam. Cheap means fiberglass. But to answer your question, adding a bit of fluff to the attic won't hurt.

G

SWEI

GW said:

High performance means spray foam.

I beg to differ. High performance (from an insulation standpoint) can be achieved using a fairly wide range of materials, but whatever it is must installed in such a way as to eliminate gaps, voids, and other opportunities for air leakage. I don't enjoy working with or around dense-packed fiberglass, but it actually performs quite well.

Cheap means fiberglass

Change that to fiberglass batts and I'll concur.

Larry Weingarten

Hello: There is a home performance contractor here in California, up by Mount Shasta, that knows how to install fiberglass batts so they actually perform! He's been teaching people for years just how to do it, but most all materials have their place. A thin coating of spray foam to insulate, but primarily air-seal is good when topped by cellulose or fiberglass. Personally, cellulose and caulk work well for me... and they don't itch!

Yours, Larry

GW

Ahh you're right, Batts are the entry level. However it's hard to expect fiberglass to act as an air barrier

SWEI

When it's truly dense-packed, it starts to work like one. Wet-spray cellulose kicks it's a$$, but either handily beats 95% of what's being installed by default in this country.

GW

yes, can we agree the foam is best, or no??? the foam can creep into cracks and crevices like no other form of insulation.

SWEI

The chemistry of spray foam is fundamentally unfriendly to living things and the "closed cell" varieties are still not not 100% closed, so they will eventually accumulate water. The R-value degrades over time regardless. I would not install it in my own house.

GW

ahhh water getting in is another problem all together.

Jamie Hall

And anything pretty much assumes that you can reliably get into the walls without damage... when you're dealing with two century old wood lath and plaster with two inches or air space and post and beam structure with odd braces everywhere...

Sigh...

Gordy

I think an assembly of 1" of of foam to seal then dense back, but is only achievable in new construction.

SWEI said:

When it's truly dense-packed, it starts to work like one. Wet-spray cellulose kicks it's a$$, but either handily beats 95% of what's being installed by default in this country.

Wall cavity air filters.

Sadly the energy could missed the construction boom when subdivisions went up like ant hills.

SWEI

XPS (and to a lesser degree EPS) sheet foam is wonderful stuff -- properly applied.