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super20g 02-22-2012 08:49 AM

Re-Insulate Bonus Room over Garage
I have a home built ~20 years ago with a bonus room over the garage and typical heat loss issues.

Money and time are a concern so I am more interested in adding to and tweaking the exisiting system.

Here are a few pictures and descriptions of what I inherited.

R-3 Foamboard and vinyl siding over that on ends. *Pay no attn to the piece of scrap plywood laying against the kneewall, the builders must have boxed themselves in before removing it, Ugh.

R-3 Foamboard over chimey framing. R-19 on other side where in contact with finished space only.

Batt's blocking off ventilation from eaves. Prior DIY fix attempt I suppose looking at the crude installation. Guess they didnt even have a carpenters knife.

R-30 on kneewalls, no rigid foam or facing to stop air penetration. R-30 adequate for Southeast region?

Ceiling is R-30 batt (I believe) and blown in fiberglass on top. No baffles for air movement. Can see dirty insulation in most areas where it wants to draw upward. Ridge vent across roofline.

View from the eaves after removing soffit to look around. Wide open going into the garage ceiling/bonus room floor.

The first 5 or so feet of the garage ceiling as well as the floor in the attic sections of the bonus room are wide open to air movement and fully uninsulated on both sides. Not enough elbow room to pull the batt insulation to see how they insulated the rest of this space. Looks like batt insulation across the garage ceiling and wrapped upward and stamped to the framing.

Typical on a frosty morning.

super20g 02-22-2012 08:51 AM

So far I have came up with:

• Remove the batt’s to unblock the eaves to allow airflow.

• Add rigid plastic rafter baffles from the eaves up the underside of the sheathing to the ridge vent. Gonna be tricky since there is already R30 batt in place in the ceiling.

• Add foamboard to the kneewalls since unblocking the eaves will allow for air movement and I do not want air movement to enter unfaced insulation. Either that or if R30 isn't adequate for Indiana and this isn't a terrible idea, might run R-13 horizontally with facing out and tape the seams.

• Blow fiberglass loose fill in the garage ceiling where it is currently uninsulated 5 ft on each side of the garage. Sprayfoam not in the budget. Only access is removing the soffit from outside so I think batt's are also out. I suppose I will not be able to insulate the underside of the bonus room attic floor, not sure if that is a big deal? Suppose I could lay 2" foamboard on top if it would be beneficial.

• Also going to block off the entry to the garage ceiling at the soffit area with foamboard. No need for air movement in there, not sure why they left it open other than material cost savings and what you can't see the homeowner won't know?

Sound like a fair plan? Any other assessment or ideas?

joecaption 02-22-2012 08:54 AM

What I can see is there is a moisture issue going on. The OSB is starting to punk up, there's fungus growing on the wood.
Looks like some piled up the insulation covering up the soffit vents, a huge no no.

super20g 02-22-2012 09:20 AM


Originally Posted by joecaption (Post 860069)
What I can see is there is a moisture issue going on. The OSB is starting to punk up, there's fungus growing on the wood.

What you see is building material and some excrement from prior pests. No moisture or mold issue.

Gary in WA 02-22-2012 09:35 PM

Find and air seal the attic leaks.

Housewrap the knee-wall.

Define the air/thermal barrier.

Clean the soffit screens, add ridge venting if needed.


Windows on Wash 02-23-2012 09:31 AM


That is about as good a picture I have ever seen to illustrate the issues with improper ventilation.

Gary's links are just about everything you would need but please post up as questions arise.

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