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Spray foaming the slopes of my attic Post New Topic | Post Reply
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Rikus
Posted: Oct 22, 2016 12:56 AM
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Spray foaming the slopes of my attic
I live right on the boarder of IECC 4 and 5(10-20 miles at most) so I want to count my house as 5 because I would rather go over than under my needs. I want to condition my attic for energy efficiency and so I can use it as conditioned storage space. I have talked to three different spray foam installers two are attached to an HVAC company and one is independent(at least how I was introduced to them). I live in a condo so I own the studs in they own the studs out so I was told my best bet is to use two inch rigid foam board and then one inch closed cell spray foam on top of the boards. This way if they decide to replace the roof next year and take the sheathing away for whatever reason my foam doesn't go away with it(there is no visible rotting in the attic now on the sheathing). Also I would have the bays and eaves in the attic open still so the room could breath and then I would still have my conditioned storage space(attic fan would just be unhooked and left there). I did get permission to spray foam my attic from the condo association, but as I've gotten further down this process companies have wanted to just spray six inch open cell foam right on the sheathing and then use paint as the thermal barrier from the inside. The things I plan to keep in the attic are glassware holiday decorations because I won't have the space anywhere else in the house and I don't want the things to degrade from the temperature extremes in an unconditioned attic. So my biggest questions what is my best long term solution that the condo association will be happy with, keep my storage needs met, and not rot my roof off because it can't breathe. Of the three contractors I have met only one has said I need to remove the fiberglass insulation on my attic floor so I don't have two layers of insulation in the house. Do I need to do this and if so can I replace them with mineral wool (Ruxul safe 'n' sound batt) for an extra sound and fire barrier since mineral wool says their product offers minimal temperature insulation. What would you recommend is my best long term solution and what kind of spay foam do I want to use? The contractors are also spay foaming the sill plate in my garage and in the basement but I would just use the same spray foam as in the attic. Also can you tell me the fire properties of open cell vs. closed cell foam? Will the paint work as a thermal barrier or I could use mineral wool stapled onto the spay foam worst case scenario. I really don't want to drywall the spray foam, tape, and paint the attic. I really want to do what is best for my house I plan to live here 15 more years, and I want to be up codes even if my town doesn't use them yet.
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mason
Posted: Oct 22, 2016 06:05 PM
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Gerald, OK, I see a bunch of questions in your post. Lets start with the easy one first. 1. How much insulation do I need to comply with building codes? The 2012 International Residential Codes require R 49 in attics in zones 4 and 5. So, it doesn't matter whether you are in zone 4 or 5. closed cell SPF has an R value ranging from 6 to 6.8 per inch depending on the brand. Open cell SPF (1/2 lb per cubic ft) has around 3.5-4 per inch, Expanded polystyrene foam board is around 4 per inch. Extruded polystyrene foam board close to 5 per inch and polyisocyanurate foam board around 6.2. In order to obtain the R 49 you would need 7-8 inches of closed cell SPF, 12-14 inches of 1/2 lb SPF. The suggested 2 inches of insulation foam board plus 1 inch of closed cell SPF will only give you from a low of R 14 (EPS foam board) to a high of R 24 (polisocyanurate foam board) Roger Morrison wrote a great article on determining insulation thickness that I can send to you. Email me masonknowles@aol.com 2. What fire protection is required on the foam? Since you are using the space for storage, then it requires a thermal barrier over the foam. It doesn't matter which foam you use. This can be either drywall, or a coating that has been tested and approved with the specific foam that you are using. Paint will not do. Contact the material supplier and ask for their ICC evaluation report on their foam. It will tell you what coatings are tested and approved and what thickness is required. For example, most SPF foams are tested with DC 315 to a thickness ranging from 10 to 15 dry mils over the foam to be an alternative to the thermal barrier. For more information go to spray foam.org and look up the technical document on thermal and ignition barriers 3. Do I take out the existing insulation on the floor of the attic and/or replace it with mineral wool? No, insulation on the floor of the attic works against the effectiveness of the insulation on the underside of the roof deck, plus can lead to increased moisture in the attic. Don't do it. 4. Will foam sprayed to the underside of the roof deck rot my roof? No, this is a myth perpetuated by other insulation groups. Properly installed, closed cell foam will not cause condensation or trap water in the sheathing. It becomes part of the sheathing and actually seals water leaks that might otherwise get into the attic by filling small cracks and holes in the sheathing. As for taking out the roof deck later. Taking out the decking will take out the sprayed foam even if it is sprayed over a foam board. You would have to re-insulate anyway. Email me and I will send you some articles on the proper use of SPF in attics. masonknowles@aol.com 5. I think you want an vented attic space that is conditioned. Not sure how that can be accomplished. You can vent the roof deck by installing insulated baffles to the underside of the roof deck and connecting them to your soffits. Then spray foam over the b |
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mason
Posted: Oct 22, 2016 06:05 PM
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Gerald, OK, I see a bunch of questions in your post. Lets start with the easy one first. 1. How much insulation do I need to comply with building codes? The 2012 International Residential Codes require R 49 in attics in zones 4 and 5. So, it doesn't matter whether you are in zone 4 or 5. closed cell SPF has an R value ranging from 6 to 6.8 per inch depending on the brand. Open cell SPF (1/2 lb per cubic ft) has around 3.5-4 per inch, Expanded polystyrene foam board is around 4 per inch. Extruded polystyrene foam board close to 5 per inch and polyisocyanurate foam board around 6.2. In order to obtain the R 49 you would need 7-8 inches of closed cell SPF, 12-14 inches of 1/2 lb SPF. The suggested 2 inches of insulation foam board plus 1 inch of closed cell SPF will only give you from a low of R 14 (EPS foam board) to a high of R 24 (polisocyanurate foam board) Roger Morrison wrote a great article on determining insulation thickness that I can send to you. Email me masonknowles@aol.com 2. What fire protection is required on the foam? Since you are using the space for storage, then it requires a thermal barrier over the foam. It doesn't matter which foam you use. This can be either drywall, or a coating that has been tested and approved with the specific foam that you are using. Paint will not do. Contact the material supplier and ask for their ICC evaluation report on their foam. It will tell you what coatings are tested and approved and what thickness is required. For example, most SPF foams are tested with DC 315 to a thickness ranging from 10 to 15 dry mils over the foam to be an alternative to the thermal barrier. For more information go to spray foam.org and look up the technical document on thermal and ignition barriers 3. Do I take out the existing insulation on the floor of the attic and/or replace it with mineral wool? No, insulation on the floor of the attic works against the effectiveness of the insulation on the underside of the roof deck, plus can lead to increased moisture in the attic. Don't do it. 4. Will foam sprayed to the underside of the roof deck rot my roof? No, this is a myth perpetuated by other insulation groups. Properly installed, closed cell foam will not cause condensation or trap water in the sheathing. It becomes part of the sheathing and actually seals water leaks that might otherwise get into the attic by filling small cracks and holes in the sheathing. As for taking out the roof deck later. Taking out the decking will take out the sprayed foam even if it is sprayed over a foam board. You would have to re-insulate anyway. Email me and I will send you some articles on the proper use of SPF in attics. masonknowles@aol.com 5. I think you want an vented attic space that is conditioned. Not sure how that can be accomplished. You can vent the roof deck by installing insulated baffles to the underside of the roof deck and connecting them to your soffits. Then spray foam over the b |
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mason
Posted: Oct 22, 2016 06:06 PM
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Gerald, OK, I see a bunch of questions in your post. Lets start with the easy one first. 1. How much insulation do I need to comply with building codes? The 2012 International Residential Codes require R 49 in attics in zones 4 and 5. So, it doesn't matter whether you are in zone 4 or 5. closed cell SPF has an R value ranging from 6 to 6.8 per inch depending on the brand. Open cell SPF (1/2 lb per cubic ft) has around 3.5-4 per inch, Expanded polystyrene foam board is around 4 per inch. Extruded polystyrene foam board close to 5 per inch and polyisocyanurate foam board around 6.2. In order to obtain the R 49 you would need 7-8 inches of closed cell SPF, 12-14 inches of 1/2 lb SPF. The suggested 2 inches of insulation foam board plus 1 inch of closed cell SPF will only give you from a low of R 14 (EPS foam board) to a high of R 24 (polisocyanurate foam board) Roger Morrison wrote a great article on determining insulation thickness that I can send to you. Email me masonknowles@aol.com 2. What fire protection is required on the foam? Since you are using the space for storage, then it requires a thermal barrier over the foam. It doesn't matter which foam you use. This can be either drywall, or a coating that has been tested and approved with the specific foam that you are using. Paint will not do. Contact the material supplier and ask for their ICC evaluation report on their foam. It will tell you what coatings are tested and approved and what thickness is required. For example, most SPF foams are tested with DC 315 to a thickness ranging from 10 to 15 dry mils over the foam to be an alternative to the thermal barrier. For more information go to spray foam.org and look up the technical document on thermal and ignition barriers 3. Do I take out the existing insulation on the floor of the attic and/or replace it with mineral wool? No, insulation on the floor of the attic works against the effectiveness of the insulation on the underside of the roof deck, plus can lead to increased moisture in the attic. Don't do it. 4. Will foam sprayed to the underside of the roof deck rot my roof? No, this is a myth perpetuated by other insulation groups. Properly installed, closed cell foam will not cause condensation or trap water in the sheathing. It becomes part of the sheathing and actually seals water leaks that might otherwise get into the attic by filling small cracks and holes in the sheathing. As for taking out the roof deck later. Taking out the decking will take out the sprayed foam even if it is sprayed over a foam board. You would have to re-insulate anyway. Email me and I will send you some articles on the proper use of SPF in attics. masonknowles@aol.com 5. I think you want an vented attic space that is conditioned. Not sure how that can be accomplished. You can vent the roof deck by installing insulated baffles to the underside of the roof deck and connecting them to your soffits. Then spray foam over the b |
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mason
Posted: Oct 22, 2016 06:06 PM
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Gerald, OK, I see a bunch of questions in your post. Lets start with the easy one first. 1. How much insulation do I need to comply with building codes? The 2012 International Residential Codes require R 49 in attics in zones 4 and 5. So, it doesn't matter whether you are in zone 4 or 5. closed cell SPF has an R value ranging from 6 to 6.8 per inch depending on the brand. Open cell SPF (1/2 lb per cubic ft) has around 3.5-4 per inch, Expanded polystyrene foam board is around 4 per inch. Extruded polystyrene foam board close to 5 per inch and polyisocyanurate foam board around 6.2. In order to obtain the R 49 you would need 7-8 inches of closed cell SPF, 12-14 inches of 1/2 lb SPF. The suggested 2 inches of insulation foam board plus 1 inch of closed cell SPF will only give you from a low of R 14 (EPS foam board) to a high of R 24 (polisocyanurate foam board) Roger Morrison wrote a great article on determining insulation thickness that I can send to you. Email me masonknowles@aol.com 2. What fire protection is required on the foam? Since you are using the space for storage, then it requires a thermal barrier over the foam. It doesn't matter which foam you use. This can be either drywall, or a coating that has been tested and approved with the specific foam that you are using. Paint will not do. Contact the material supplier and ask for their ICC evaluation report on their foam. It will tell you what coatings are tested and approved and what thickness is required. For example, most SPF foams are tested with DC 315 to a thickness ranging from 10 to 15 dry mils over the foam to be an alternative to the thermal barrier. For more information go to spray foam.org and look up the technical document on thermal and ignition barriers 3. Do I take out the existing insulation on the floor of the attic and/or replace it with mineral wool? No, insulation on the floor of the attic works against the effectiveness of the insulation on the underside of the roof deck, plus can lead to increased moisture in the attic. Don't do it. 4. Will foam sprayed to the underside of the roof deck rot my roof? No, this is a myth perpetuated by other insulation groups. Properly installed, closed cell foam will not cause condensation or trap water in the sheathing. It becomes part of the sheathing and actually seals water leaks that might otherwise get into the attic by filling small cracks and holes in the sheathing. As for taking out the roof deck later. Taking out the decking will take out the sprayed foam even if it is sprayed over a foam board. You would have to re-insulate anyway. Email me and I will send you some articles on the proper use of SPF in attics. masonknowles@aol.com 5. I think you want an vented attic space that is conditioned. Not sure how that can be accomplished. You can vent the roof deck by installing insulated baffles to the underside of the roof deck and connecting them to your soffits. Then spray foam over the b |
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mason
Posted: Oct 22, 2016 06:06 PM
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Gerald, OK, I see a bunch of questions in your post. Lets start with the easy one first. 1. How much insulation do I need to comply with building codes? The 2012 International Residential Codes require R 49 in attics in zones 4 and 5. So, it doesn't matter whether you are in zone 4 or 5. closed cell SPF has an R value ranging from 6 to 6.8 per inch depending on the brand. Open cell SPF (1/2 lb per cubic ft) has around 3.5-4 per inch, Expanded polystyrene foam board is around 4 per inch. Extruded polystyrene foam board close to 5 per inch and polyisocyanurate foam board around 6.2. In order to obtain the R 49 you would need 7-8 inches of closed cell SPF, 12-14 inches of 1/2 lb SPF. The suggested 2 inches of insulation foam board plus 1 inch of closed cell SPF will only give you from a low of R 14 (EPS foam board) to a high of R 24 (polisocyanurate foam board) Roger Morrison wrote a great article on determining insulation thickness that I can send to you. Email me masonknowles@aol.com 2. What fire protection is required on the foam? Since you are using the space for storage, then it requires a thermal barrier over the foam. It doesn't matter which foam you use. This can be either drywall, or a coating that has been tested and approved with the specific foam that you are using. Paint will not do. Contact the material supplier and ask for their ICC evaluation report on their foam. It will tell you what coatings are tested and approved and what thickness is required. For example, most SPF foams are tested with DC 315 to a thickness ranging from 10 to 15 dry mils over the foam to be an alternative to the thermal barrier. For more information go to spray foam.org and look up the technical document on thermal and ignition barriers 3. Do I take out the existing insulation on the floor of the attic and/or replace it with mineral wool? No, insulation on the floor of the attic works against the effectiveness of the insulation on the underside of the roof deck, plus can lead to increased moisture in the attic. Don't do it. 4. Will foam sprayed to the underside of the roof deck rot my roof? No, this is a myth perpetuated by other insulation groups. Properly installed, closed cell foam will not cause condensation or trap water in the sheathing. It becomes part of the sheathing and actually seals water leaks that might otherwise get into the attic by filling small cracks and holes in the sheathing. As for taking out the roof deck later. Taking out the decking will take out the sprayed foam even if it is sprayed over a foam board. You would have to re-insulate anyway. Email me and I will send you some articles on the proper use of SPF in attics. masonknowles@aol.com 5. I think you want an vented attic space that is conditioned. Not sure how that can be accomplished. You can vent the roof deck by installing insulated baffles to the underside of the roof deck and connecting them to your soffits. Then spray foam over the b |
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mason
Posted: Oct 22, 2016 06:08 PM
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I was cut off from the rest of the answer. 5. I think you want an vented attic space that is conditioned. Not sure how that can be accomplished. You can vent the roof deck by installing insulated baffles to the underside of the roof deck and connecting them to your soffits. Then spray foam over the baffles. Only problem with this technique is that the baffles need to stay open while you spray the foam over them. If you close of the air flow then it ends up allowing moist air into the space under the deck from the outside without being able to vent it out, making the situation worse not better. I would rather spray directly to the underside of the roof deck and make an unvented roof deck. Again, I can forward some nice articles on vented vs unvented attics. 6. Can I use mineral wood on the attic floor to increase fire resistance and sound proof between floors? The drywall ceiling of your floor of the attic is a code designated fire resistant thermal barrier. I am not sure you are going to gain much more fire resistance by adding the mineral wool. As for soundproofing between the floors, mineral wool, cellulose and blown in fiberglass are good sound absorbers, but, what sound are you trying to minimize from the attic? Since adding this insulation will reduce your energy efficiency and work against the insulation to the underside of the roof deck, I would not recommend it. 7. Which spray foam should I use? This is a question I am often asked. 1/2 SPF is cheaper by the R value per inch, but requires a vapor retarder over the foam in colder climates (such as zone 5). It has a higher permeance which allows water vapor to more easily pass through it. Closed cell SPF has a lower permeance and does not require an additional vapor retarder over it in any of the US climate zones. Closed cell SPF adds structural strength to the substrate and will increase wind uplift resistance of the roof deck (2 to 3 times over conventionally fastened roof decks). So, if high winds, tornados or hurricanes are an issue, then closed cell adds that benefit over 1/2 lb SPF. Crunch the numbers and see which makes the most sense in your environment and climate. You can call me to discuss further 571-239-5221 Mason |
