Insulation, Radiant and Vapor Barriers - Insulating Basement Block Walls
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gabe24
02-16-06, 04:18 PM
My home is a split foyer, the first floor is half below grade on the front and slopes slowly down to a full walkout to the grade at the back of the home.
My question is I'm gutting my 1st floor because of an electrical remodel and I want drywall instead of wood paneling. When I took down a peice of the paneling to see what I was working this I found sporadic r-9 unfaced batts with a vapor barrier torn in sections directly on the block. This level of the house is always cold 10 degrees colder. I'd like to redo the insulation in these walls and seal it up. Ive come up with two options but I'm not sure what order the matterials would go in. The walls are masonary block with a 3" gap and then 2x4 walls.
1) Use 2" Ridgid Foam, with all joints sealed and taped. Then r-13 unfaced batts in the walls cavity. Would a vapor barrier be needed with the foam? Or would the foam be the vapor barrier if all joints are sealed?
2) Have a contractor spray foam all the walls with 2" 's of foam. Then insulate with r-13 unfaced. Would a vapor barrier be used here?
thanks,
Roy
My question is I'm gutting my 1st floor because of an electrical remodel and I want drywall instead of wood paneling. When I took down a peice of the paneling to see what I was working this I found sporadic r-9 unfaced batts with a vapor barrier torn in sections directly on the block. This level of the house is always cold 10 degrees colder. I'd like to redo the insulation in these walls and seal it up. Ive come up with two options but I'm not sure what order the matterials would go in. The walls are masonary block with a 3" gap and then 2x4 walls.
1) Use 2" Ridgid Foam, with all joints sealed and taped. Then r-13 unfaced batts in the walls cavity. Would a vapor barrier be needed with the foam? Or would the foam be the vapor barrier if all joints are sealed?
2) Have a contractor spray foam all the walls with 2" 's of foam. Then insulate with r-13 unfaced. Would a vapor barrier be used here?
thanks,
Roy
Concretemasonry
02-16-06, 08:33 PM
Before you go off and decide the only solution is to improve your basement comfort is to put more insulation on the walls, look at the big picture.
You need less insulation below grade than you need above grade because the temperature different between warm and cold is much different in the winter. Your soil/concrete is always above 40 to 50 degrees and the outside air temperature can be down to -30 depending where you are.
In the summer, less insulation in a basement is a benefit because the the thermal tempertature moderation provided by the soil.
You probably have more heat loss through your uninsulated floor than you do through the walls, since the temperature at the bottom of a wall averages about the same as the temperature of the floor.
Most below ground floor areas are cold because of poor air circulation and a lack of properly located air suplies and RETURNS. This is the reason for your 10 degree differential between the upstairs and downstairs. You are not getting the cold air out, so the warm air cannot circulate. I have a 2 degree difference (interior wall at 5 feet up) with an UNDER-INSULATED lower level due to good air control, adequate low returns and a DC variable speed furnace fan. My laser thermometer reads minimum temperatures at the fireplace surface at 54 and the floor surface at the slider at 48. My low heating bills in Minnesota are low because of the type of structure, but I have never been over $95 per month for a 1400 sf 3 BR townhouse for heat and hot water. This includes the $8.00 minimum connection fee. - In the summer, the cooler basement return air reduces my air conditioning costs.
Get your heating and cooling squared away before you insulate and then decide on the best strategy. - P.S. R-values do not mean much since that is only a rate of heat loss, not a real measure of building insulation.
Dick
You need less insulation below grade than you need above grade because the temperature different between warm and cold is much different in the winter. Your soil/concrete is always above 40 to 50 degrees and the outside air temperature can be down to -30 depending where you are.
In the summer, less insulation in a basement is a benefit because the the thermal tempertature moderation provided by the soil.
You probably have more heat loss through your uninsulated floor than you do through the walls, since the temperature at the bottom of a wall averages about the same as the temperature of the floor.
Most below ground floor areas are cold because of poor air circulation and a lack of properly located air suplies and RETURNS. This is the reason for your 10 degree differential between the upstairs and downstairs. You are not getting the cold air out, so the warm air cannot circulate. I have a 2 degree difference (interior wall at 5 feet up) with an UNDER-INSULATED lower level due to good air control, adequate low returns and a DC variable speed furnace fan. My laser thermometer reads minimum temperatures at the fireplace surface at 54 and the floor surface at the slider at 48. My low heating bills in Minnesota are low because of the type of structure, but I have never been over $95 per month for a 1400 sf 3 BR townhouse for heat and hot water. This includes the $8.00 minimum connection fee. - In the summer, the cooler basement return air reduces my air conditioning costs.
Get your heating and cooling squared away before you insulate and then decide on the best strategy. - P.S. R-values do not mean much since that is only a rate of heat loss, not a real measure of building insulation.
Dick