I just inspected a house with open-cell foam in the attic on the roof deck and framing, along with loose fill on the ceiling. To my mind, this either could cause condensation problems, or at best, the loose fill is unnecessary. Also, I am inclined to recommend air exchange up there, but don’t want to stir up a fuss without being absolutely sure. Anyone out there with specific experience on this issue care to help me out a little bit?
There is a lot more involved in spray foaming an attic than just other insulation in use. Since we know nothing of the attic you inspected your best course of action is to Google the subject, read the proper methods and caveats to spray foaming an attic, review how this attic space is configured and used, and then determine how many issues might exist.
I have read many pages of information by Joe Lstiburek (sp?) who seems to be a leading specialist. I have read a lot of information in general on the subject. What I wanted to know was if anyone had encountered similar situations and what they recommended–or didn’t recommend. I am aware that the latest research indicates that when an attic is sealed with foam and is not ventilated (typical of foam sealing) as this one was, that air exchange is recommended. What I wanted to know was if anyone actually recommends air exchange in an attic that is un-vented and sealed with foam. My apologies for not being much more specific; this is a communicative deficit that comes through from time to time.
I Can not advise you but you might get some help from Here All the best Roy
In the homes that I have inspected that had Icynene installed on the roof sheathing and top chords…(some old and some new but all very expensive homes)…I consulted with one of the design mechanical engineers about this issue.
I was concerned that the home was not designed for the additional cubic footage and other indirect loads.
His answer was that there was more than enough energy savings to compensate for the additional area and there was enough leakage to partially condition the additional space.
Because he indicated that the leakage helped in the design…I would think that the loose fill on the ceiling should be removed. I can not think of a reason for it but I think you would be well advised to ask the designer of the system…or the insulators…but I believe you have a valid question.
Does spray foam insulation need a fire retardant cover in the attic?
Wood rafters/trusses & roof sheathing will burn with or without insulation.
The r value of that foam is likely somewhere around r24 if open cell and 6 inches +/- thick. If the ceiling is insulated to r40, no one is going to want to remove 66% of their r value. As far as an insulator, the dead space is an amazing insulator and would make a very efficient ceiling. I can’t however give you an educated answer on conditioning the space. An fresh in and stale out hrv duct would definitely be my advice and makes sense, however I don’t have actual data or code to back that up. That’s how any other sealed or encapsulated space would be treated, however those are typically conditioned or heated spaces. I look forward to reading some of the other replies on this post.
Spray Foam Insulation: Open and Closed Cell
This attic is now considered part of the homes living space in a way. The outside perimeter is now insulated and sealed just like a wall. The insulation on the ceiling joists would be like insulating the floor of the home. Considering it this way helps to figure it out really. You now have a conditioned space that should have proper air flow to keep humidity at bay. An air exchanger of some sort is a must.
http://buildingscience.com/documents/digests/bsd-149-unvented-roof-assemblies-for-all-climates
](http://buildingscience.com/)
Building Science Corporation
[LIST]
[/LIST]
You are here
- Home
- » Building Science Digests
- » BSD-149: Unvented Roof Assemblies for All Climates
BSD-149: Unvented Roof Assemblies for All Climates
Christopher Schumacher
July 24, 2007
**Abstract: **
Unvented roof assemblies, such as conditioned attics and unvented cathedral ceilings, are becoming common in North American construction. These assemblies are created by eliminating ventilation openings and moving the thermal, moisture and air control boundaries to the plane of the roof deck. This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction
Hopefully there’s air damns between the roof decking and the top of the insulation (if it’s open cell, which it appears to be) :s
Interesting Why how does this help.
Yes, the Icynene should have a fire retardant spray applied.
How can we know this is done does it show that it has been done .
It’s vapor permeable and needs an air space. Open cell against roof sheathing has been found to cause damp sheathing.
Interesting can you show me a web site to confirm this info …Thanks
Alot of good info there… thanks;-)
To all who have pitched in, thank you. Special thanks to you, Roy, I have begun reading the materials you sent links to, and am re-discovering that it has a lot to do with climate zones as to what provisions get made. They say you have to read a yard of material on a subject to be considered an expert, so I have 2 feet 9 inches to go. Also thanks to you, Marvin, for your perspective; I am in a similar climate, so this is useful.