DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Insulation and Radiant Barriers > Insulation help in attic/half story




Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old 04-16-2010, 06:14 AM  
swindmill
Senior Member
 
Join Date: Jan 2010
Posts: 167
Liked 12 Times on 11 Posts
Likes Given: 1

Default

Bathroom: You've definitely talked me into tearing out the rest of the drywall and starting over with insulation. I'm guessing I'll need to put some sort of stop (drywall, plywood) behind the framing of the knee wall so that I can put polystyrene there as well. I'll do at least 5 inches, 6 if feasible, along the knee wall, sloped ceiling, and top attic so the room is completely incased in it. I'll have to work around the recessed lighting and fan of course.

Closet: Should I do the same thing with the closet? Incase the room in 6 inches of polystyrene? I could then just add lose insulation to the area of the attic that remains unfinished and vent it properly.

Bedroom: While I'm a big fan of doing things right, I just can't tear down all that drywall and have to rehang, refinish, and repaint that entire space. I'm thinking about having an insulation company come out and look into blowing additional insulation in behind those walls and into the top attic. Doing that (if it's possible?) along with properly insulating the closet and unfinished attic space would be a big improvement, I would think.


If I'm going to do the foam board in the bathroom and closet, would it make sense to have a spray foam contractor come out and spray foam those two rooms, or would that be a lot more expensive than doing the boards myself? Thanks for the help.



__________________
swindmill is offline  
 
Reply With Quote Quick reply to this message
Old 04-17-2010, 04:40 AM  
Perry525
Senior Member
 
Perry525's Avatar
 
Join Date: Apr 2010
Location: Lake Wales, Fl.
Posts: 110
Liked 9 Times on 6 Posts

Default

If you cut the foam as a push tight fit, then it will stay in place without any backing.

Yes the idea is to have a complete polystyrene box, that is both air and water vapour tight.

With the lights and fan, use some cans of spray, to keep the total integrity.

Keep in mind, for the fan to do its job it needs to pull air from somewhere, so that it is pushed outside with the water vapour.
If there is no air supply the fan will struggle to clear the room. I normally suggest that an extractor fan with a heat exchanger be used as you get a balanced flow, with the incoming air being warmed by the extracted air.....but, in your case venting through the roof...it may not be possible.

Yes. The problem with water vapour (that which is not expelled by the fan) is that it always makes for the coldest spot to condense, these spots are the toilet cistern, the windows and any spots like the closet, where there is no warm air circulating. Result, damp, mould, wood rot, smells. Not good.

Finish the bathroom and closet, see how it goes through the summer, then think about the rest of the job and decide when you are sure.

The spray foam, you can do it yourself, and will probably take more care and do a better job.(and it will be cheaper) Ask around you may find a good price, watch out for a cheap price and someone who doesn't do the job properly.
If you do get someone in, stand there and watch them do the job, do not go away and leave them to it. After all its your money and you have to live with the result.



__________________
Perry525 is offline  
 
Reply With Quote Quick reply to this message
Old 04-19-2010, 11:31 AM  
swindmill
Senior Member
 
Join Date: Jan 2010
Posts: 167
Liked 12 Times on 11 Posts
Likes Given: 1

Default

Thanks for the advice. I'm going to look into the spray foam option and weigh it against the Polystyrene option. I'll do one of the two in the next month or so. Waiting on the bedroom is a good idea. Hopefully it will feel better with the closet and bathroom done.

__________________
swindmill is offline  
 
Reply With Quote Quick reply to this message
Old 04-20-2010, 03:36 AM  
Perry525
Senior Member
 
Perry525's Avatar
 
Join Date: Apr 2010
Location: Lake Wales, Fl.
Posts: 110
Liked 9 Times on 6 Posts

Default

May I add one more recommendation.
Buy an infrared temperature gauge.
With this you can hold the trigger and scan anything and it will tell you its surface temperature.
Use it to measure the temperature of the walls in the bathroom and closet after you have finished.
Then read the temperatures of the rest of the attic that are "as now."
This will show you what you have achieved and what remains to be done.

__________________
Perry525 is offline  
 
Reply With Quote Quick reply to this message
Old 05-25-2010, 01:34 PM  
swindmill
Senior Member
 
Join Date: Jan 2010
Posts: 167
Liked 12 Times on 11 Posts
Likes Given: 1

Default

The closet mentioned above is framed in and ready for insulation. I'm still debating on what exactly to do to keep it cooler up there. The roof joists are about 5" deep and 24" apart. From reading up on this issue, I'm led to believe that I really need a radiant barrier against the actual roof, before putting in insulation. Is this true?

If so, based on cost and limited space, I'm thinking about doing the ceiling of the closet in this order: roof|radiant barrier|R-19|3/4" polystyrene board over the joists|drywall

That'll give me R-23 plus the radiant barrier, which isn't great but unless I give up ceiling height it seems to be about the best I can do, taking cost into account.

My main objective is to combat the extreme heat upstairs. Since knocking the wall out for the closet, it's so incredibly hot up there that I literally start sweating within 30 seconds of walking up the stairs.

__________________
swindmill is offline  
 
Reply With Quote Quick reply to this message
Old 05-26-2010, 06:50 AM  
Perry525
Senior Member
 
Perry525's Avatar
 
Join Date: Apr 2010
Location: Lake Wales, Fl.
Posts: 110
Liked 9 Times on 6 Posts

Default

Fix two layers of 2 inch thick polystyrene between the rafters. With staggered close fitting joints. Cut them to a push tight fit.
Two inch thick is easy to cut with a knife.
If you go for one four inch thick layer cutting with and old saw will be easier, but more messy.
Stick a radiant barrier on the top sheets, carefully leaving a one inch gap between the top of the polystyrene/radiant barrier and the underneath of the roof, this will enable the radiant barrier to reflect the suns radiation back up through the roof.
The polystyrene between the rafters, will stop the hot convection currents transmitting the heat from the roof through to the drywall.
Then fix another layer of polystyrene across the rafters, this will stop the conducted heat that arrives in the room via the, roof and the wooden rafters.
Then fix the drywall screwing through the drywall/polystyrene into the rafters.
The result, a one inch gap, a reflective layer, five inches of polystyrene, one layer of drywall.

__________________
Perry525 is offline  
 
Reply With Quote Quick reply to this message
Old 05-26-2010, 10:54 AM  
swindmill
Senior Member
 
Join Date: Jan 2010
Posts: 167
Liked 12 Times on 11 Posts
Likes Given: 1

Default

I noticed that Lowe's sells a polystyrene board with a radiant barrier affixed to each side of the foam. I think it's called "perma-R" or something similar. Could I use that in place of the radiant barrier and first polystyrene board?

The old roof joists are all about 4 inches deep. They are not consistent in depth (and so not level), and 4 inches isn't deep enough, so I'll have to sister something to the inside of each joist. I imagine any gaps or cracks this creates can be addressed with a can foam insulation.

Is there any need for a vapor barrier on the outside of all of this?

One last question: Should I insulate the attic ceiling all the way down to where it meets the floor, and insulate the knee wall. Or, should I only insulate the knee wall? It is a 100 year old home and does not have soffit venting. It has only one gable vent, which really doesn't do much of anything. The space left unfinished is really just the side attic behind the knee walls. Should I just go ahead and insulate everything rather than worry about how to properly ventilate the little space that remains?

__________________

Last edited by swindmill; 05-26-2010 at 12:06 PM.
swindmill is offline  
 
Reply With Quote Quick reply to this message
Old 05-27-2010, 03:01 AM  
Perry525
Senior Member
 
Perry525's Avatar
 
Join Date: Apr 2010
Location: Lake Wales, Fl.
Posts: 110
Liked 9 Times on 6 Posts

Default

By all means use a board with a radiant barrier on both sides, only the side facing the sun will reflect the suns radiation.

Five inches of polystyrene will reduce an outside temperature of 95f to about 74f on the inside.
Yes blocking all gaps does make a difference. As I mentioned earlier once a convection current starts up it can move an incredible amount of heat from one side to the other. Foam is ideal for filling odd shaped holes.
The purpose of an vapour barrier is to stop the water vapour created inside the home, by cooking, washing and breathing getting into the walls and rotting the wood. A vapour barrier is always positioned under the drywall.
Polystyrene is windproof and waterproof (in as much as continuous immersion in water will result in a 3 to 4% take up of water) In your location, the fact that it is warm, makes polystyrene a useful vapour barrier. (Provided there are no holes)
Yes, to get the maximum benefit of your work, the whole room should be protected by at least five inches of polystyrene.

Keep in mind that the heat that will arrive inside the room, will mainly come by conduction via the roof, rafters and the small amount of polystyrene covering the rafters. If you measure the length of the framing to the room, the width and the total amount of square feet of wood covered by your proposed 3/4 inch polystyrene and divide that into the total square footage of the ceiling and walls, you will be surprised how large this weak area is, and what an impact it will have on the rooms temperature.

One inch of polystyrene with a temperature on one side of 126f will show about 98f on the other, from this you can see that the wood of the rafters will end up being the weak link, two inches as a cover of polystyrene is better.

The purpose of roof ventilation is based on an incorrect premiss.

The theory is that the wind blowing over a home will create an area of low pressure to the lee of the home. This will then suck the air from the attic and remove any water vapour that has infiltrated from the home below.
This will remove the likelihood of ice forming during the winter.
The fact is there are many days/nights when there is no wind.

During the summer, the theory is, the wind will remove the heat from the attic.
When on many days there is no wind. And in any event the heat is transmitted via conduction through the framing and radiation.

So yes! The more and thicker the insulation, the less heat will get through to the room.

If you have south facing windows, then an outside shutter, will be a great benefit, shading the room and keeping the radiation out.

__________________
Perry525 is offline  
 
Reply With Quote Quick reply to this message
Old 05-27-2010, 11:35 AM  
swindmill
Senior Member
 
Join Date: Jan 2010
Posts: 167
Liked 12 Times on 11 Posts
Likes Given: 1

Default

Then I'll plan on insulating the entire space, finished and unfinished, and then insulating the knee walls as well. I was going to change my plans a bit to include sistering 2x6's to the ceiling joists so that I have 5.5" of space for insulation. If I were to do that, I wouldn't have enough room to also put 2" of polystyrene on the outside of the 2x6's. 2x4's provide slightly less depth than the existing joists. So, I'd have to come up with some combination of material that puts the depth at 4.5". I'm thinking I could put a 1/2" polystyrene board with the radiant barrier in and then the 2x4 on top of that...but that just seems a bit unconventional. The bottom line is that 5.5" of insulation is about as much as I can do before putting up the drywall, otherwise I will be sacrificing too much head space, which is very limited as it is.

__________________
swindmill is offline  
 
Reply With Quote Quick reply to this message
Old 05-28-2010, 11:51 AM  
Perry525
Senior Member
 
Perry525's Avatar
 
Join Date: Apr 2010
Location: Lake Wales, Fl.
Posts: 110
Liked 9 Times on 6 Posts

Default

The only time you can get a job 100% right is with a new build.
Renovation is always about compromise.



__________________
Perry525 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


Similar Threads
Thread Thread Starter DIY Home Repair Forum Replies Last Post
Half Work Half Dont.....going nuts! guz168 Electrical and Wiring 4 10-14-2009 07:38 PM
Half Work Half Dont guz168 Electrical and Wiring 3 09-01-2009 07:13 AM
Attic insulation worth it??? waimeamike Green Energy and Sustenance Living 5 07-31-2009 07:39 PM
Yet Another Attic Insulation Advice WishIKnew Green Energy and Sustenance Living 4 02-20-2009 08:28 AM
Attic insulation casualfc General Home Improvement Discussion 1 08-12-2008 12:32 PM