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Hy Cheese Posted: Jul 06, 2008 07:30 PM	Not another attic question I read just about every post on this forum and still am needing some advice (even read all the articles on your site). I bought an older home in need of much work in south western Kentucky, moved into last December and wore long johns for 3 months straight - no heat except wood burner. I decided to insulate before doing any other remodeling, the exterior walls will be no problem with foam because they will be stripped to the studs, the ceiling attic is a difference of opinion though. I can do the floor of my attic for about $400 in cellulose R40 or about $700 with foam and cellulose, but thats not the question. I have a 7/12 pitch and have a usable 8'x26' strip down the middle that makes a great storage room, spraying and glassing the roof deck would cost about $2000 and be quite a task getting to the eves. This is my final resting place and have no need for a real conditioned space in the attic, and may never use it to boot but what are your thoughts on enclosing the 8x26 with walls and just spraying that, the sides of the attic would be all cellulose. My main concern is comfort and cost of utilities on the main floor with air conditioning being the major factor not any extra storage in the attic. Note the roof is not really vented even though there are 2 small gable vents the soffit is solid, I can address that if needed because all the fascia needs replacing. It is also 80 degrees in the house, 105 in the attic and about 90 outside, no air conditioning running. Thanks, cb
Gerry Wagoner Posted: Jul 06, 2008 11:24 PM	What is the depth of the attic floor joists? A reasonable solution might be to fill the cavity under the attic storage deck with foam. That exploits the advantage of spray foam, creating lots of insulation in a small space. best wishes, oG
mason Posted: Jul 07, 2008 08:00 AM	The most efficient way to insulate the house is to spray foam to the underside of the roof deck in an unvented configuration. (note; check with your shingle manufacturer on warranties, some shingle manufacturers do not allow unvented insulated attics in their warranties, studies contradict these exclusions but it is a factor nonetheless to consider). The other method I would consider is to spray the floor of the attic. I would not create different climate zones within the attic by boxing off the sides of the attic and insulating with cellulose. You have the potential for strong convection currents plus potential for condensation within the attic space that is not insulated with sprayfoam. Some things to consider, if you have HVAC equipment or ductwork running through your attic, the unvented attic configuration would be the most cost effective solution in the long term. If you do not have HVAC equipment or ductwork and can effectively seal off the living space from the attic by spraying foam on the floor of the attic, that might be the most cost effective solution over the long term. If you choose this route, additional ventilation would be required in the attic. (based on your earlier description of your attic space, the ICC codes describe the type of ventilation and amount required based on area of your attic space.) Hope this helps.
richard cozzolino cozzolino Posted: Jul 14, 2008 11:50 AM	Hi I have a house built in 1956 with a vented attic with one gable vent on one side the other side has a little door about 3 feet wide by 4 tall that connects with a conditioned room,I can get in there easily and the floor of the attic is 27x35 its not to big but i can walk in there, I have air conditiong ducts and tubing up there that i sprayfoamed. the temp in the summer is above 100 degres the ducts cover much of the floor. there is blown in insulation on the floor of the attic which is uncovered it would be difficult to take the insulation off the attic floor and re spray with foam. i have hot water heating for the winter and central air in the house for the summer and I live in CT. The AC is always on when its hot taking the moisture out of the air but in the winter i have hot water heat but nothing to take the moisture out of the air. My question is do you think i will have problems if i sray under the roof with closed cell im not worried about the shingles. im looking for ideas. Here are a few I was thinking of (1) Seal under the shingles with 2 inch of CC and keep gabel vent. (2) spray more than 2 inchs of CC under roof seal and foam gabel vent and make the roof air tight, and if nesasarry put a dehumidifier in the attic. or should i leave the 3X4 door open to the conditioned space.(3) just leave things the way they are. Thanks for any ideas on the subject. Rich
mason Posted: Jul 16, 2008 08:09 AM	You are thinking too much on the issue. Consider this only. What are the temperature ranges in the attic and the highest possible humidity. Right now if you have 70 degree F temperature inside the house and its 20 degrees F outside, your attic temperature would be around 25 degrees F. If your humidity inside the house is 60%, the dewpoint would be 48 degrees F. So, the warm humid air going into the attic would condense on a lot of surfaces. Then you are relying on the air movement to dry it out. Now, lets say you seal the attic and spray 4 inches of SPF to the underside of the roof deck. Your interior temperature still at 70 degree F and 60% humidity. But, your attic temperature is now around 62 degrees F. The dewpoint under those circumstances is 48 degrees F. You are well above dewpoint temperature. So, the unvented attic controls moisture condensation much better by eliminating the dewpoint in the attic space. Hope this helps.
richard cozzolino cozzolino Posted: Jul 16, 2008 12:32 PM	Thank you mason Im still not sure if i under stand, if I spray 4 inchs of CC can I leave the celulose insuation in the attic floor (almost impossible to remove due to AC ducts) and do i need to leave that 4x3 door open for air circulation or will the condinsation never form because of the 4 inches of CC. Thanks Rich
mason Posted: Jul 16, 2008 02:52 PM	You don't need the door open for circulation,plus leaving it open to the conditioned space makes the attic space into conditioned space requiring a thermal barrier over the foam rather than an ignition barrier. As for the blown in insulation, it is not doing any good on the floor of the attic. It will make the attic space a little bit colder and probably has a lot of crud that has been filtered through it over the years. I would remove it if at all possible.
richard cozzolino cozzolino Posted: Jul 16, 2008 03:22 PM	Do you think its worth me doing and safe if i dont remove the old insulation because of all the duct work. Thanks Rich
mason Posted: Jul 21, 2008 08:26 AM	It would be allright, just not quite as effective and as I said the existing insulation probably has a lot of crud stuck in it over the years (dirt, mold, leaves, mouse droppings, etc)

Author

Comments

Hy Cheese

Posted: Jul 06, 2008 07:30 PM

Not another attic question

I read just about every post on this forum and still am needing some advice (even read all the articles on your site).

I bought an older home in need of much work in south western Kentucky, moved into last December and wore long johns for 3 months straight - no heat except wood burner.

I decided to insulate before doing any other remodeling, the exterior walls will be no problem with foam because they will be stripped to the studs, the ceiling attic is a difference of opinion though.

I can do the floor of my attic for about $400 in cellulose R40 or about $700 with foam and cellulose, but thats not the question. I have a 7/12 pitch and have a usable 8'x26' strip down the middle that makes a great storage room, spraying and glassing the roof deck would cost about $2000 and be quite a task getting to the eves.

This is my final resting place and have no need for a real conditioned space in the attic, and may never use it to boot but what are your thoughts on enclosing the 8x26 with walls and just spraying that, the sides of the attic would be all cellulose. My main concern is comfort and cost of utilities on the main floor with air conditioning being the major factor not any extra storage in the attic.

Note the roof is not really vented even though there are 2 small gable vents the soffit is solid, I can address that if needed because all the fascia needs replacing. It is also 80 degrees in the house, 105 in the attic and about 90 outside, no air conditioning running.

Thanks,
cb

Gerry Wagoner

Posted: Jul 06, 2008 11:24 PM

What is the depth of the attic floor joists? A reasonable solution might be to fill the cavity under the attic storage deck with foam. That exploits the advantage of spray foam, creating lots of insulation in a small space.

best wishes,

oG

mason

Posted: Jul 07, 2008 08:00 AM

The most efficient way to insulate the house is to spray foam to the underside of the roof deck in an unvented configuration. (note; check with your shingle manufacturer on warranties, some shingle manufacturers do not allow unvented insulated attics in their warranties, studies contradict these exclusions but it is a factor nonetheless to consider).

The other method I would consider is to spray the floor of the attic. I would not create different climate zones within the attic by boxing off the sides of the attic and insulating with cellulose. You have the potential for strong convection currents plus potential for condensation within the attic space that is not insulated with sprayfoam.

Some things to consider, if you have HVAC equipment or ductwork running through your attic, the unvented attic configuration would be the most cost effective solution in the long term.

If you do not have HVAC equipment or ductwork and can effectively seal off the living space from the attic by spraying foam on the floor of the attic, that might be the most cost effective solution over the long term. If you choose this route, additional ventilation would be required in the attic. (based on your earlier description of your attic space, the ICC codes describe the type of ventilation and amount required based on area of your attic space.)

Hope this helps.

richard cozzolino cozzolino

Posted: Jul 14, 2008 11:50 AM

Hi I have a house built in 1956 with a vented attic with one gable vent on one side the other side has a little door about 3 feet wide by 4 tall that connects with a conditioned room,I can get in there easily and the floor of the attic is 27x35 its not to big but i can walk in there, I have air conditiong ducts and tubing up there that i sprayfoamed. the temp in the summer is above 100 degres the ducts cover much of the floor. there is blown in insulation on the floor of the attic which is uncovered it would be difficult to take the insulation off the attic floor and re spray with foam. i have hot water heating for the winter and central air in the house for the summer and I live in CT. The AC is always on when its hot taking the moisture out of the air but in the winter i have hot water heat but nothing to take the moisture out of the air. My question is do you think i will have problems if i sray under the roof with closed cell im not worried about the shingles. im looking for ideas. Here are a few I was thinking of (1) Seal under the shingles with 2 inch of CC and keep gabel vent. (2) spray more than 2 inchs of CC under roof seal and foam gabel vent and make the roof air tight, and if nesasarry put a dehumidifier in the attic. or should i leave the 3X4 door open to the conditioned space.(3) just leave things the way they are. Thanks for any ideas on the subject. Rich

mason

Posted: Jul 16, 2008 08:09 AM

You are thinking too much on the issue. Consider this only. What are the temperature ranges in the attic and the highest possible humidity.

Right now if you have 70 degree F temperature inside the house and its 20 degrees F outside, your attic temperature would be around 25 degrees F.

If your humidity inside the house is 60%, the dewpoint would be 48 degrees F. So, the warm humid air going into the attic would condense on a lot of surfaces. Then you are relying on the air movement to dry it out.

Now, lets say you seal the attic and spray 4 inches of SPF to the underside of the roof deck. Your interior temperature still at 70 degree F and 60% humidity. But, your attic temperature is now around 62 degrees F. The dewpoint under those circumstances is 48 degrees F. You are well above dewpoint temperature.

So, the unvented attic controls moisture condensation much better by eliminating the dewpoint in the attic space.

Hope this helps.

richard cozzolino cozzolino

Posted: Jul 16, 2008 12:32 PM

Thank you mason
Im still not sure if i under stand, if I spray 4 inchs of CC can I leave the celulose insuation in the attic floor (almost impossible to remove due to AC ducts) and do i need to leave that 4x3 door open for air circulation or will the condinsation never form because of the 4 inches of CC. Thanks Rich

mason

Posted: Jul 16, 2008 02:52 PM

You don't need the door open for circulation,plus leaving it open to the conditioned space makes the attic space into conditioned space requiring a thermal barrier over the foam rather than an ignition barrier. As for the blown in insulation, it is not doing any good on the floor of the attic. It will make the attic space a little bit colder and probably has a lot of crud that has been filtered through it over the years. I would remove it if at all possible.

richard cozzolino cozzolino

Posted: Jul 16, 2008 03:22 PM

Do you think its worth me doing and safe if i dont remove the old insulation because of all the duct work. Thanks Rich

mason

Posted: Jul 21, 2008 08:26 AM

It would be allright, just not quite as effective and as I said the existing insulation probably has a lot of crud stuck in it over the years (dirt, mold, leaves, mouse droppings, etc)

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