DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Insulation and Radiant Barriers > Why is my house so Hot!?!




Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old 05-24-2011, 05:34 PM  
oldognewtrick
Moderator
HRT_MODERATOR.png
 
oldognewtrick's Avatar
 
Join Date: Jul 2009
Location: Nashville, TN
Posts: 5,413
Liked 459 Times on 382 Posts
Likes Given: 146

Default

Power vents work well when they are working, but they have a tendency to burn the motors out after 6-8 years. Ventilation is a 2 part equation and exhaust vents will only be functional if you have intake ventilation to support it.



__________________
oldognewtrick is offline  
 
Reply With Quote Quick reply to this message
Old 05-25-2011, 03:18 AM  
Perry525
Senior Member
 
Perry525's Avatar
 
Join Date: Apr 2010
Location: Lake Wales, Fl.
Posts: 112
Liked 11 Times on 7 Posts

Default

I wonder why the fixation on the roof ventilation?

Yes you can replace the hot air in the attic with more hot air from outside, yes if you stand in the path of blown air, because it removes the moisture/sweat from your skin you feel cooler, but this does not effect/lower the heat that is conducted and radiated from the outside through the frame and into your home.

Wood doesn't have feelings, it doesn't feel cooler because hot air is blowing past, like we do!

If you want an exhaust fan to cool, it must be pulling colder air from somewhere, and how will it find cold air when the source is roof height?

And....what effect does an exhaust fan in the roof have on the heat arriving through your walls? Will it be pulling cooler air from inside the home, that will be replaced by hotter air from outside.

To get the desired effect, you must block the sun, grow some shade, paint the roof silver or white to reflect the radiation, insulate.

To have a miner effect the cold air source must at least arrive from the shaded part of the home, preferably at ground level.

Powerful exhaust fans cost a lot to buy, they cost a lot to run and if the replacement air supply into the roof space is not easily available, constricted supply, then they are always struggling to pull outside air into the roof and they quickly burn out.



__________________
Perry525 is offline  
 
Reply With Quote Quick reply to this message
Old 05-25-2011, 05:48 AM  
oldognewtrick
Moderator
HRT_MODERATOR.png
 
oldognewtrick's Avatar
 
Join Date: Jul 2009
Location: Nashville, TN
Posts: 5,413
Liked 459 Times on 382 Posts
Likes Given: 146

Default

Perry, I agree with you. Fixation on ventilation is about replacing very hot air with less hot air. I've been in attics that have been in the 130's and it takes your breath away to crawl through them. If you allow the very hot air to escape and replace it with outside air you can decrease the temperature in the attic and reduce the convection into the house. Vent MFG's recommend setting the fans at about 112'.

I am a roofing contractor by trade and have had men working on non-ventilated roof decks that have had structural failure from heat, not water. Extremely high temps will cause the wood structure to dry out to the point of being brittle. Plywood will de-laminate and turn into cardboard. Rafters will crack and split. Wood may not have feelings but it sure doesn't like a hot/dry environment to live in.

Is ventilation a perfect solution for reducing heat transfer into a structure? NO. Can the average homeowner afford to retrofit their homes to near perfect conditions. Probably not. Sometimes, better is the best we can hope for.

__________________
oldognewtrick is offline  
 
Reply With Quote Quick reply to this message
Old 05-27-2011, 05:50 PM  
nealtw
Contractor
 
Join Date: Nov 2010
Location: vancouver, b.c.
Posts: 10,260
Liked 847 Times on 756 Posts
Likes Given: 1463

Default

In extreme heat of the attic the lumber drys out and with out venting it stays in the attic air untill the weather changes and all that moisture is deposited back on surface of the insulation and lowers its R value. When your in an attic at 130 degrees that hot air from out feels pretty cool. Lumber was a living thing and it will live a long time if it is treated like it has feelings.

__________________
nealtw is offline  
 
Reply With Quote Quick reply to this message
Old 05-28-2011, 04:55 AM  
Perry525
Senior Member
 
Perry525's Avatar
 
Join Date: Apr 2010
Location: Lake Wales, Fl.
Posts: 112
Liked 11 Times on 7 Posts

Default

Quote:
Originally Posted by nealtw View Post
In extreme heat of the attic the lumber drys out and with out venting it stays in the attic air until the weather changes and all that moisture is deposited back on surface of the insulation and lowers its R value. When your in an attic at 130 degrees that hot air from out feels pretty cool. Lumber was a living thing and it will live a long time if it is treated like it has feelings.
========================

I agree that timber gets hot, whether or not it dries is down to the relative humidity at the time.

From the time the timber leaves the kiln it starts to adapt to the average relative humidity where it is, this means increased water content during the winter/rain season and drier during the summer/dry season, obviously while the amount of water in the air varies every 24 hours between the hottest day periods and the coldest nights and the high water vapor/relative humidity levels during the night and the lows during the day there is a general drift towards drier or wetter.

I think you are writing that the moisture from the wood, stays in the attic until the weather changes with the arrival of winter or summer?

I regret to write that I disagree your comments.

This is not possible. As relative humidity levels move as day changes to night and night to day with the changes in temperature.

The way water vapor/moisture works is that it always moves towards a colder place or surface or an area of lower pressure.

The surface temperature of the insulation in the attic will be at the same temperature as the air in the attic, most of the time.

You only get condensation, when warm wet air arrives from inside the home or from outside and the timber in the attic is cold and the surface of the insulation is cold.

Cold meaning below the Dew Point of the incoming air. Then condensation or frost is likely to form.

Most of the year, when the temperature of the attic is not below the Dew Point of the incoming warm wet air, water vapor leaves the attic and moves outside, where it is almost always cooler, and if the wind is blowing it will be at a lower air pressure, as the wind always creates an area of low pressure to the lee of a building.

The problem with fiberglass and cellulose, so called insulation, is that warm wet/humid air leaves the home, rising through the insulation, and as it does so it freezes, later the ice melts, makes the insulation wet and useless, and this provides an express route out for your expensive heat, as water is 4,000 times better at conduction heat from your home than is dry air.

This is why closed cell insulation's like Styrofoam/Blueboard/polystyrene etc are so much better in real life as they do not get wet inside, they can be covered in ice and yet they still do their job of insulating your home.
__________________
Perry525 is offline  
 
Reply With Quote Quick reply to this message
Old 05-28-2011, 06:48 AM  
oldognewtrick
Moderator
HRT_MODERATOR.png
 
oldognewtrick's Avatar
 
Join Date: Jul 2009
Location: Nashville, TN
Posts: 5,413
Liked 459 Times on 382 Posts
Likes Given: 146

Default

Perry, I'm thinking Neal and I are saying warm, moist air from the house in the winter months collects in the attic and condenses the insulation. I personally like the idea of having a ventilated attic area. I think I understand the problems associated with fiberglass insulation. I'm not yet on the bandwagon with spray foam on the underside of the roof deck and creating conditioned area in the attic. My concern is if the roof leaks the homeowner will never know it until major damage has occurred to structure. As you have said, foam does not allow for transfer of moisture.

So, why does every application of spray foam have application to roof deck and not to the area in between the ceiling joists? It shouldn't be that difficult to fabricate a hatch to have access into the attic that seals. When we do flat roof installations, we sometimes add poly-ISO board and flat roofs are not usually vented. With a shingle roof you would basically have a structure over a flat roof if you sprayed in between the ceiling joists.

__________________
oldognewtrick is offline  
 
Reply With Quote Quick reply to this message
Old 05-29-2011, 09:50 PM  
nealtw
Contractor
 
Join Date: Nov 2010
Location: vancouver, b.c.
Posts: 10,260
Liked 847 Times on 756 Posts
Likes Given: 1463

Default

Perry your absolutly right about moister moving outside, If the roof is venting properly. I believe the house should be treated as a living, breathing beast. When they get hot with no air they swet just like people in mine shaft. If you could completely seal of an area like an attic with out air the whole top of the house would be shot in about five years. But that,s just me!!

__________________
nealtw is offline  
 
Reply With Quote Quick reply to this message
Old 05-31-2011, 10:12 PM  
ConcreteTreat
Concrete/Basement Guru
 
Join Date: May 2011
Location: Branford, CT
Posts: 14
Default

Quote:
Originally Posted by oldog/newtrick View Post
Welcome to House Repair Talk. Yes you need to install ventilation and probably insulation. Ventilation will work as intake at the lowest point on the roof and exhaust at the highest. Call a couple roofing contractors and get a professional opinion of what will be required to provide a proper ventilation system.
Forgive me if I'm making a fool out of myself...

BUT.

Ventilation AND Insulation? If you have an insulated box that's ventilated, it would no longer have value as an insulated box. How is this different with a house?


-----

Gale
Concrete Treat: Concrete Sealer
__________________
ConcreteTreat is offline  
 
Reply With Quote Quick reply to this message
Old 06-01-2011, 05:34 PM  
nealtw
Contractor
 
Join Date: Nov 2010
Location: vancouver, b.c.
Posts: 10,260
Liked 847 Times on 756 Posts
Likes Given: 1463

Default

Concrete Treat, The venting is out side of the insulation so the box or attic has freash air and the house is still an insulated box.

__________________
nealtw is offline  
 
Reply With Quote Quick reply to this message
Old 06-01-2011, 08:16 PM  
ConcreteTreat
Concrete/Basement Guru
 
Join Date: May 2011
Location: Branford, CT
Posts: 14
Default

Quote:
Originally Posted by nealtw View Post
Concrete Treat, The venting is out side of the insulation so the box or attic has freash air and the house is still an insulated box.
OH! I understand now. Thank you!

And call me Gale. :-)


__________________
ConcreteTreat is offline  
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On