Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 08-23-2010, 09:08 AM   #1
Newbie
 
Join Date: Aug 2010
Posts: 5
Rewards Points: 10
Default

Adding Attic Insulation


I live in Japan where I bought a house that's about 15 years old. The codes and standards for construction are quite different; in fact the entire house building culture is different. The good thing is that it is basically an American style house built for a climate similar to upstate New York.

Both my heating and cooling costs are astronomical and I have begun the process of retrofitting insulation, sealing wall outlets, installing self-adhesive foam insulation to my windows and so on.

The next project and the one I think will make the most noticeable difference is sealing the attic, completely, and adding some insulation to it. It would be nice to rent a blower and add 20 inches of insulation to the existing, but that's not an option. My options are limited to: fiberglass rolls or blue polystyrene rigid foam sheets.

My only question, for now, is: can I just add the blue polystyrene on top of the existing fiberglass insulation?

barneyrubble is offline   Reply With Quote
Old 08-23-2010, 09:23 AM   #2
Member
 
Join Date: Feb 2010
Location: MI's Western UP
Posts: 599
Rewards Points: 500
Default

Adding Attic Insulation


the advantage of the blue foam is R per inch at the expense of cost.
you normally don't deal with space limitations in an attic.

What I've heard that having the foam and glass together glass sugests what you are planning might cause mold to form on the glass.

The rolls sound like the best available option for you on both accounts.

dealing with fiberglass isn't that bad at all. wear cheap gloves and and old longsleave shirt and pants, glasses and painting mask might be nice too.


Last edited by forresth; 08-23-2010 at 09:25 AM.
forresth is offline   Reply With Quote
Old 08-23-2010, 01:50 PM   #3
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Rewards Points: 2,000
Default

Adding Attic Insulation


"My only question, for now, is: can I just add the blue polystyrene on top of the existing fiberglass insulation?" ----- Yes.
I would air seal the attic first as you said: http://www.rd.com/how-to-seal-attic-...icle18158.html
This will stop the stack effect of heated air escaping there: http://www.wag-aic.org/1999/WAG_99_baker.pdf
The attic is like a wall on its side, attic side equals outside:
“Foam board insulation is commonly placed between the exterior finish (i.e., siding, brick) and the studs of exterior walls. To prevent air infiltration, you should place rigid insulation boards tightly together and seal the seams with tape or caulk. However, this practice may worry some builders in cold climates since the foam board may act as a second vapor diffusion retarder. Studies have shown, however, that condensation rarely occurs in these areas unless something else is seriously wrong with the wall assembly (i.e., massive uncontrolled air leakage into the walls from the house). If the assembly is constructed correctly, the inside surface of the foam board stays warm enough to keep water vapor in its gaseous state long enough for it to escape.” Bolding is mine, from: http://www.energysavers.gov/your_hom.../mytopic=11620

Board over the loose fill is similar to this:
“One of the final experiments included the additional layer of a 1-in. unfaced fiber-glass insulation 'blanket' (density of 1 lb/ft3) over the loose-fill insulation. Thermal resistance increased 12 to 16%, with a heat flow of 10-13% lower than the results with the pillow in place. The blanket was actually or slightly more effective than the pillow. This is believed to be due to the blanket having a slightly larger thermal resistance and/or air flow resistance due to its higher density. (see Figure 5.)” Bolding is mine, from: http://www.homeenergy.org/archive/he...92/920510.html

R-38 required in attic for NY. http://www.ornl.gov/cgi-bin/cgiwrap?...le/ins_fact.pl

The problem is installing batts perfectly. Keep them level with the ceiling framing to install the next rows perpendicular to the first. No air tunnels above or next to the tops of the joists to negate the batts from wind-washing: “One of the heat exchange mechanisms that cavity insulations are intended to control is convection. When convective looping is able to occur in or around the insulation, its function is subverted. Also, air moving through insulation because of wind or other pressures can also subvert its performance. Therefore, low density fibrous insulations should be covered by air barriers in areas subject to air movement.
Rolled Batt Insulation: Batt insulation can be a very cost effective option where the framing cavities are of uniform size and where the width and depth matches that of the rolled batt insulation. With rolled batt insulation care must be taken to cut the insulation to fit snugly in cavities and around all obstructions without compression. When batts are cut too short, too narrow, or too wide around obstruction, gaps and the associated problems result. Also when batts have been cut too big for the cavity or have not been cut to adequately accommodate obstructions there will tend to be compression and gaps of incomplete thickness (“rolled shoulders” at framing or wrinkles in the field of the batt). Compressing batt insulation also reduces its thermal resistance (effectively, its R-value). Batts should also be fluffed to full thickness so that they will be in contact with the cavity enclosure on all six sides and not leave gaps for convective looping. Higher density rolled batts are more effective at inhibiting convective looping within the insulation.” From: http://www.buildingscience.com/docum...archterm=insul
Use foam boards at exterior wall line: http://www.homeenergy.org/archive/he...96/961110.html


Be safe, Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Reply


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 Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Attic insulation johndeer General DIY Discussions 6 01-21-2010 08:59 PM
Adding Insulation - getting around in attic VelvetFoot Building & Construction 2 11-13-2009 01:49 PM
Idea for attic insulation baffles. What are your thoughts? Ininkus Building & Construction 8 02-26-2009 12:46 PM
Adding insulation to only a portion of an attic? curls00 Building & Construction 22 10-27-2008 09:41 AM
Attic Insulation Quote...what do you think? mitchel Roofing/Siding 15 08-06-2008 07:10 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.