From $9.95


Statistics

Users
Total: 32,900
Visited Last 30 days: 227
Forum Messages
Total: 20,966
Last 30 days: 7
Forum Evaluations
Total: 24,160
Last 30 days: 0
Journal Entries
Total: 5,400
Last 30 days: 10
Connections
Total: 15,247
Last 30 days: 4
Downloads
Total: 87,196

Journals

Name
NorthShoreBathrooms
7 Visits | 1 Posts | 2 Pix | 0 Videos
Tenants-Right-When-S... Maryland, MD
585 Visits | 5 Posts | 4 Pix | 0 Videos
furnacerepairon St Catharines, AL
27 Visits | 1 Posts | 9 Pix | 0 Videos
furnacemkm Markham, AL
29 Visits | 1 Posts | 7 Pix | 0 Videos
vallejocleaningservi... Vallejo , CA
25 Visits | 1 Posts | 1 Pix | 0 Videos
getpestcontrol Delhi, AL
33 Visits | 1 Posts | 1 Pix | 0 Videos
noithattrieugia tphcm, AL
49 Visits | 1 Posts | 0 Pix | 0 Videos
httpownerbuilderbook...
115 Visits | 1 Posts | 0 Pix | 0 Videos
Packers-and-Movers Delhi, AL
376 Visits | 2 Posts | 1 Pix | 0 Videos
Best-Access-Doors Jackson, AL
164 Visits | 1 Posts | 0 Pix | 0 Videos
Concrete-Contractors...
225 Visits | 2 Posts | 0 Pix | 0 Videos
bird Springfield, MO
166 Visits | 1 Posts | 0 Pix | 0 Videos
Tanglewood Colorado Springs, CO
120,366 Visits | 1,004 Posts | 2,581 Pix | 47 Videos
Drywall-Repair-Lehi
241 Visits | 1 Posts | 0 Pix | 0 Videos
ianpundt
277 Visits | 1 Posts | 0 Pix | 0 Videos
Magic-Of-The-SideSto... San Carlos, CA
604 Visits | 2 Posts | 2 Pix | 0 Videos
httpswwwfaxitfastcom... salt lake city, AL
249 Visits | 1 Posts | 0 Pix | 0 Videos
Owning-My-First-Prop... Grand Rapids, MI
358 Visits | 1 Posts | 0 Pix | 0 Videos
movers-and-packers Hyderabad, AL
350 Visits | 1 Posts | 1 Pix | 0 Videos
Investment-Propertie... Rochester, MN
400 Visits | 1 Posts | 0 Pix | 0 Videos
See all journals...

Current Top-Rated Posters

RatingPosts
Lance in Buena Vista, CO0.002

Thank you, Mark and Elaine.
Cary O., Menifee, CA

Try one of our new Construction Bargain Strategies for free. Coupon code: CBS. One strategy could save you $1,000 or $10,000 or maybe $50,000 when you build or remodel.
25,000 pages of free owner-builder resources.  We accept no ads.

Spray foam on ceiling joist instead of rafters?


Filter by date: and/or Keyword



Reply... Subscribe to this topic


Bill's Forum Posts: 64
Interview Answers: 15

Private Message


Randomly Selected Image

Login to Vote

By Bill in Callahan, FL on 1/29/2006


Is is allowed or recommended to seal your house from your attic using a thinner layer of spray foam against the joist and then place blown-in insulation over it? Has anyone seen it done or seen any documentation?

Bill


Reply...


Norman's Forum Posts: 5
Interview Answers: 4

Private Message


Randomly Selected Image

Login to Vote

By Norman in Waxhaw, NC on 2/21/2006


Hello Bill:

The DIY Channel has a show that reported on a 4,000 sf home and they used that insulation treatment. There are two schools of thought.

1-Don't do it... The air needs to move from the attic to the outside to prevent humidity to build up between the shingles and the underlayment. Also the increased heat in the summer could create increased humidity to get trapped in between.

2-Check this link and it should add a lot of answers to your concerns diynetwork.com/diy

BTW... I intend to use this on my outer walls.

Good luck.


Reply...


Tom's Forum Posts: 160
Interview Answers: 156

Private Message


Randomly Selected Image

Login to Vote

By Tom in Stroudsburg, PA on 2/22/2006


Bill,

I have to disagree with Norman, but there are conditions. It sounds to me like you wish to spray the top side of the sheetrock from inside the attic. That would be acceptable. You cannot spray the bottom side of your sheathing, which is what I think Norman was trying to say.

#1 You cannot spray if you are using trusses, as they recommend these float. 

#2 Do not, I repeat, DO NOT spray your soffit area, as Norman said, your attic must be able to breathe.

Soffit, gable vents, exhaust fans and ridge vents are there for this reason. More specifically, the area between the insulation and roof sheathing must be able to breathe.

#3 Close any gaps between your joists and the sheetrock.

If the spray foam gets in there, it may push the sheetrock away from the joist. This will not matter structurally, but you may notice unevenness in your ceiling when viewed from your living space. The last time I checked, spray foam was $1 per sq ft per 1" thickness, but that was when gas was only $1.25, and spray foam is a petroleum byproduct.
Reply...


Norman's Forum Posts: 5
Interview Answers: 4

Private Message


Randomly Selected Image

Login to Vote

By Norman in Waxhaw, NC on 2/27/2006


Tom:

Just to clarify...

I am uncertain what you are disagreeing with? If you re-read what I said, I clearly did not say anything about the underlayment of the roof. The material is sprayed to "outer" walls in an unclosed wall. It then expands to fill the crevice and once finished expanding excess is "shaved off" using a special tool to allow for sheetrock installation.

Several well-known home energy studies have been doing some testing of this material (it's all over the Web if you do some research) and claims that it can be used in the underlayment of the roof, but there has not been enough time to determine the true experience for a clear outcome. I do not and DID not recommend it in my previous post. I wanted Bill to have some more info on this and that is the reason for the link.

With traditional building there must be an air gap in the attic to allow humidity to escape from the attic. If you are going to use blown-in insulation, a special barrier is used under the roof to allow air to travel and insulation to be placed within the wall. Check your R-value of the materials available to make the best choice. 

To answer the next question, it does not make sense to use expanding insulation and then blown-in insulation. The expansion is mostly uncontrolled, and "thin" sprays seldom stay thin.


Reply...


Tom's Forum Posts: 160
Interview Answers: 156

Private Message


Randomly Selected Image

Login to Vote

By Tom in Stroudsburg, PA on 2/27/2006


Norman,

It was definitely a good link and noteworthy. If someone wants to build rooms or make their attic conditioned space, it is certainly a viable option. I wonder if the shingles would last without the air flow on the underside of the roof and if the shingle manufacturers would stand behind their warranty?

I was not debating the cost effectiveness of what Bill was asking, but he did ask if he could spray his joists as opposed to rafters. Other than providing him with a "don't do it", I merely pointed out the potential pitfalls if he did do it. One other use that is quite common in Florida is the application on the roof exterior (mostly commercial) as an insulation and waterproofing. It then gets painted (U/V shielding).
Reply...


Norman's Forum Posts: 5
Interview Answers: 4

Private Message


Randomly Selected Image

Login to Vote

By Norman in Waxhaw, NC on 2/27/2006


Hello:

I understand now. They use this (similar) product on some roofs in commercial applications in Puerto Rico. I believe that if this product is used and humidity is not allowed to properly escape, the paneling under the shingles will deteriorate, and possibly allow warping, thus the shingles can "rip". This warping (created by water being trapped within the wall) will create excessive "pull" on the shingles creating a "failure” of the shingles. They can get ripped off by wind as they "expand and contract" over the roof. Also there could be a mold problem if the humidity is high and lasts long enough. I don’t recommend it for a roof.

I know for a FACT what humidity does to improper air flow problems in attics. I love the R-value the expanding foam provides and also the wind flow resistance, especially where electrical conduits are.

 


Reply...


Brian's Forum Posts: 26

Private Message


Randomly Selected Image

Login to Vote

By Brian in AK on 2/27/2006


Do some research. There are people advocating sealed attics with spray-on insulation on the underside of the sheathing, and they are being built. The spray-on insulation manufacturer websites offer much information. However as mentioned, you need to make sure shingle installation allows this type of roof.
Reply...

2004, 2005, 2006 Merit Award Winner

John's Forum Posts: 278
Interview Answers: 69

Private Message


Randomly Selected Image

Login to Vote

By John in Erie, CO on 2/27/2006


My house is like that - I've applied the spray foam to the UNDERSIDE of the sheathing, creating a conditioned attic with NO roof venting. It is part of the 2004 IRC code. It works. This saved 27 or so pop vents, and the inevitable leaks/flashing that would be around each one. Plus, can lighting, etc. need not have airtight baffles built around them to keep air infiltration down.

Do lots of research - this is the new high-performance envelope (it's very common among the building science folks)... SIP roofs are exactly the same, sealed, unvented. It can have some significant HVAC and maintenance advantages over traditional methods. I did this to my house, and there are three others in the area using a similar method, even on roofs with steep pitches.

Different spray foams will have different requirements. Some closed-cell polys will require a thermal ignition barrier over them, others like biobased and Icynene will not, as their flame/smoke spread index is pretty low.

Reply...


Tom's Forum Posts: 160
Interview Answers: 156

Private Message


Randomly Selected Image

Login to Vote

By Tom in Stroudsburg, PA on 2/27/2006


John, I'm curious to know if you have a shingled roof and if you have an idea how hot the roof gets on a hot summer day? Any signs of shingles buckling? Also, the obvious questions of what kind of sq ft, thickness and cost.

Thanks.


Reply...


Steven's Forum Posts: 51
Interview Answers: 60

Private Message


Randomly Selected Image

Login to Vote

By Steven in MN on 4/3/2006


I have an attic area over my garage that I'd like to insulate and use as walk-in closet and light storage that is accessible through the wall into my master bath. It is a truss system. Roof angles directly down so no side wall height area, so the middle portion is usable. What are recommendations for this? Can I apply the spray foam on top of the garage ceiling sheetrock to fill the joist cavity and then put flooring over that? What about the soffits and roof area? I am not sure if I can enclose the whole thing, or need to leave soffits open and run venting channels up the roof on the interior.

My plan is to run electrical in there for outlets/lighting and also install drop down attic steps for secondary access to/from the attic room.

Reply...


Brian's Forum Posts: 26

Private Message


Randomly Selected Image

Login to Vote

By Brian in AK on 4/3/2006


Steven,

First thing to do is make sure that your trusses are designed to support whatever it is you plan to do with the room. They may not have been engineered to support a floor system.

Brian


Reply...


Steven's Forum Posts: 51
Interview Answers: 60

Private Message


Randomly Selected Image

Login to Vote

By Steven in MN on 4/3/2006


Thanks, yes it is a 2x4 truss system that spans a two-car garage. I was told it would hold light storage. I'd probably want to reinforce it w/a cross beam support or two. What is the rule of thumb in this situation?
Reply...


Tom's Forum Posts: 160
Interview Answers: 156

Private Message


Randomly Selected Image

Login to Vote

By Tom in Stroudsburg, PA on 4/3/2006


Steven,

Brian gives good advice but you can't go by "being told", you have to find the prints for the truss and get the loading capacity from them. If they are unavailable, measure one exactly including the size of the plates tying the pieces together. You will also need the lumber stamp info. and have a truss company tell what you can put in for loading.

Usually by light loading they mean you can put the boxes of holiday items up there, not floor systems and closets. A standard floor is designed with 40 lbs of live loading and in a full-functioning attic they want to see 30 lbs. My trusses are 2x6 and are only rated for 20 lbs. A lot of it depends on the span, the size and type of lumber, the truss webs and the size of the gusset plates.
Reply...


Steven's Forum Posts: 51
Interview Answers: 60

Private Message


Randomly Selected Image

Login to Vote

By Steven in MN on 4/3/2006


Thank you! I will get an expert opinion before doing anything. I would hate to have a 9-foot drop when getting dressed some morning!
Reply...


Bob's Forum Posts: 4
Interview Answers: 2

Private Message


Randomly Selected Image

Login to Vote

By Bob in Houston, TX on 6/4/2006


My two cents for what it's worth...

Place: Hill Country of TX... season: Texas summer... condition: hot... temp. of external roof... 118 degrees... temp. inside my sealed-in attic... 74 degrees... reason: new construction technology resulting in lower utility cost as well as less HVAC equipment...

Fact: 77% of all U.S. residential homes have more AC tonnage than they need... why: old construction technology... another suggestion:... look into hot water on demand from your newer hot water heaters... no need to keep cooking the water all day... only when you need it... all at on-demand... and no, you don't have to wait for it... it's instant.

For more information Google this.

Take care... save yourself some money.


Reply...


Shane's Forum Posts: 1

Private Message


Randomly Selected Image

Login to Vote

By Shane in Webster, TX on 7/9/2006


I would have a radiant barrier sprayed instead.
Reply...



Reply... Subscribe to this topic

Copyright 1997-2020 Consensus Group Inc.