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Needs advice Posted: Aug 16, 2016 03:58 PM	need help choosing between joist spray or eaves... I own and live in a 43 year old single dwelling on a slab, north west Texas. approx 2900 sq feet plus a 2 car attached garage. The attic is sparsely insulated with very old fiber glass and is mostly compressed.. I have high air conditioning bills and think that when my HVAC was replaced in 2000 that they upsized it as the old system was prone to freezing up. I have gotten insulation installation quotes from 2 licensed residential contractors. One suggests sucking out all the old and spraying 6 inches between the ceiling joists (attic floor) for an r value of 43. The other suggests sealing off the power vents and all the attic and spraying the underside of the roof and making the attic a part of the house envelope. He also offers after installation a "free" energy audit with a power door. There eis not that much cost difference between the two and I I have no basis for comparison to know which would be the best fit for the heating and cooling efficiency and lower energy costs. Could you please help? Thanks
mason Posted: Aug 16, 2016 05:10 PM	You could go either way depending on a couple of factors: Go unvented if you have a lot of HVAC equipment, ductwork, etc in the attic. The foam installed to the underside of the attic plus selling the vents makes the attic space within 5-8 degrees of the interior temperature. This enables your HVAC equipment and ductwork work less to maintain the correct temperature. Go vented if you do not have a lot of ductwork or HVAC equipment in the attic. Insulating the floor with foam separates the interior space from the attic space. The attic space in this scenario will get much hotter in the summer and much colder in the winter but the foam keeps the temperature from reaching the interior space. Email me at masonknowles@aol.com I can send you a copy of an article I wrote last year for Construction Specifier titled "To Vent or Not to Vent"

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Needs advice

Posted: Aug 16, 2016 03:58 PM

need help choosing between joist spray or eaves...

I own and live in a 43 year old single dwelling on a slab, north west Texas. approx 2900 sq feet plus a 2 car attached garage.

The attic is sparsely insulated with very old fiber glass and is mostly compressed..

I have high air conditioning bills and think that when my HVAC was replaced in 2000 that they upsized it as the old system was prone to freezing up.

I have gotten insulation installation quotes from 2 licensed residential contractors.
One suggests sucking out all the old and spraying 6 inches between the ceiling joists (attic floor) for an r value of 43.

The other suggests sealing off the power vents and all the attic and spraying the underside of the roof and making the attic a part of the house envelope.
He also offers after installation a "free" energy audit with a power door.

There eis not that much cost difference between the two and I I have no basis for comparison to know which would be the best fit for the heating and cooling efficiency and lower energy costs.
Could you please help?

Thanks

mason

Posted: Aug 16, 2016 05:10 PM

You could go either way depending on a couple of factors:

Go unvented if you have a lot of HVAC equipment, ductwork, etc in the attic. The foam installed to the underside of the attic plus selling the vents makes the attic space within 5-8 degrees of the interior temperature. This enables your HVAC equipment and ductwork work less to maintain the correct temperature.

Go vented if you do not have a lot of ductwork or HVAC equipment in the attic. Insulating the floor with foam separates the interior space from the attic space. The attic space in this scenario will get much hotter in the summer and much colder in the winter but the foam keeps the temperature from reaching the interior space.

Email me at masonknowles@aol.com I can send you a copy of an article I wrote last year for Construction Specifier titled "To Vent or Not to Vent"

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