Attic temps

[signal15]

For those of you with attic temp sensors, what's the highest temp you've seen? My buddy just told me his brother noticed that his house in the desert in Utah didn't have any attic vents. So he put a temp sensor up there on a relatively cool day, and it was hitting 170F. Who knows what it hit on a hot day...

You can slow cook a pork shoulder at 185 for 24 hours and end up with some really tasty pork sandwiches.

 

[Kevin L]

Youch! In my new home (SW Florida) I designed it without vents in the attic (no roof or soffit venting) and installed Icynene insulation. My attic never gets warmer than 10 degrees over the house temp. With the AC set at 78, the attic never reaches 90.

 

[hucker]

140F on a 89F say in seattle

 

[dutchyn]

In my new home (SW Florida) I designed it without vents in the attic (no roof or soffit venting) and installed Icynene insulation.

I didn't even consider not venting the attic; we have soffit and 8 roof vents. Why would one not want the attic vented?

 

[beelzerob]

Why would one not want the attic vented?

You can slow cook a pork shoulder at 185 for 24 hours and end up with some really tasty pork sandwiches

Asked and answered. (or I guess answered, THEN asked)

 

[signal15]

If you don't vent your attic in colder temps, the snow melts off the roof from the rising heat and then freezes right above the soffits, causing ice dams which can damage your shingles and back up water under them into the attic. I have about 10 roof vents, and perforated soffits, and when the wind blows outside, it howls through the attic.

It's still to damn hot up to work in the summer though.

 

[midon]

For those of you with attic temp sensors, what's the highest temp you've seen?

Record high for me was 125F before I installed an attic fan a year ago. Since then, highest ever was 108F. Air conditioning bills have also plummeted.

Located in Atlanta.

Mitch

 

[Kevin L]

In my new home (SW Florida) I designed it without vents in the attic (no roof or soffit venting) and installed Icynene insulation.

I didn't even consider not venting the attic; we have soffit and 8 roof vents. Why would one not want the attic vented?

Quieter, healthier, more energy efficient, providing your insulation is proper for an unvented attic space. For more information about the benefits, check out Icynene website.

In hurricane areas, it's also safer not to vent your attic. The vents, especially soffit vents, are some of the weakest areas of the home, allowing wind and rain into the home, and to exert extreme pressure that can collapse ceilings and cause roofs to fail. The soffits on my home are made of hardiboard covered with cementious stucco. No wind or rain intrusion.

I put a lot of thought and research into how best to design and build my home. There were a lot of items that were the first time my builder used them. The Icynene insulation is one of the best decisions.

One important item about Icynene. Your HVAC system must be designed to work with a home insulated with Icynene. I hired a contractor that was quite familiar with the changes required and made the load calcs with Icynene factored in.

Kevin

 

[Smarty]

In my new home (SW Florida) I designed it without vents in the attic (no roof or soffit venting) and installed Icynene insulation.

I didn't even consider not venting the attic; we have soffit and 8 roof vents. Why would one not want the attic vented?

Quieter, healthier, more energy efficient, providing your insulation is proper for an unvented attic space. For more information about the benefits, check out Icynene website.

In hurricane areas, it's also safer not to vent your attic. The vents, especially soffit vents, are some of the weakest areas of the home, allowing wind and rain into the home, and to exert extreme pressure that can collapse ceilings and cause roofs to fail. The soffits on my home are made of hardiboard covered with cementious stucco. No wind or rain intrusion.

I put a lot of thought and research into how best to design and build my home. There were a lot of items that were the first time my builder used them. The Icynene insulation is one of the best decisions.

One important item about Icynene. Your HVAC system must be designed to work with a home insulated with Icynene. I hired a contractor that was quite familiar with the changes required and made the load calcs with Icynene factored in.

Kevin

When your house is that sealed up, don't forget about air exchange and possible de-humidification. Most residential foam installs go cheap here...if you going to do it (using foam in the right climate), do it right, and spend a bit more and get a air exchange/dehumdification unit as well.

I live in HOT and somtimes humid San Antonio, using the above approach.

 

[kd5crs]

One important item about Icynene. Your HVAC system must be designed to work with a home insulated with Icynene. I hired a contractor that was quite familiar with the changes required and made the load calcs with Icynene factored in.

Kevin

Kevin,

Can you give any more information? What kind of changes are required to the load calculations? I have an older house that need a new upstairs A/C unit as well as pretty much all new insulation everywhere. I'm going to get a quote for using Icynene and I want to know what questions to ask.

Thanks.
Brian

 

[jharrell]

In my new home (SW Florida) I designed it without vents in the attic (no roof or soffit venting) and installed Icynene insulation.

I didn't even consider not venting the attic; we have soffit and 8 roof vents. Why would one not want the attic vented?

Venting attics in a hot climate is a fallacy, it was originally done to prevent ice damning in a cold climate, but with proper insulation that is not an issue anymore. Less than 10% of the heat energy entering your house from the roof comes from the hot attic air, the rest is radiant from the roof deck to your attic deck. Using a attic fan is even worse then passive venting as it creates a lower pressure in the attic than in the house pulling conditioned air up through any openings(light fixtures, electrical outlets, etc.) .

Modern construction is moving toward unvented attics usually with an open cell spray foam on the underside of the roof decking with no radiant barrier because now you are bringing the attic space into the building envelope and allowing hvac ducting in the attic to not be exposed to extreme temps and keeping humidity out, it is also much easier to air seal this way using spray foam then sealing the attic deck properly with normal fiber glass.

See Building Science for more information than you would ever want to know, this is the real deal. Be aware most roofers and contractors know little about this stuff and will simply do what they have always done which is the same thing going back decades.

 

[Rupp]

Here's a chart of my temps. This is about average during the summer.

 

[hucker]

Here is the last month...ignore the down time

 

[signal15]

Icynene looks really interesting. I actually do have some in portions of my basement, but I didn't know what it was called. I need to re-insulate above the garage, because my bedroom is above it, and the builder did it wrong. I get frozen pipes in the winter in my master bath.

Check out the video I found of that Icynene stuff:

http://www.youtube.com/watch?v=7BwaABLvvlI

 

[Kevin L]

One important item about Icynene. Your HVAC system must be designed to work with a home insulated with Icynene. I hired a contractor that was quite familiar with the changes required and made the load calcs with Icynene factored in.

Kevin

Kevin,

Can you give any more information? What kind of changes are required to the load calculations? I have an older house that need a new upstairs A/C unit as well as pretty much all new insulation everywhere. I'm going to get a quote for using Icynene and I want to know what questions to ask.

Thanks.
Brian

Hi, Brian.

Smarty and Jharrell touched on it. There is the air exchange consideration since you have now sealed up the house. The Trane contractor I selected knew exactly what Icynene was and how to adjust for it. In fact, he said he's been called in to correct some bad HVAC/Icynene installations. One home he was in was so tight and didn't replace with makeup air that you had difficulty opening the front door when the air was running. In addition, since the building envelope now includes the attic. I don't know what change is made to the load calcs, but there definitely is an adjustment for the no venting/Icynene setup.

When you are interviewing HVAC contractors, ask them about Icynene and gauge the reaction. If they're not sure about it, find someone that is. Plus, as suggested earlier, check out the Icynene and Building Science websites, including the PDF here.

Kevin