Save Energy

Question: Is this what you are suggesting?

Fri, 09 May 2008 09:07:39 -0500

Lynne writes again from Clinton, Ohio and sends another drawing: "I am a little confused. Can you look at the attached and tell me if this is what you are suggesting? Can't really lay insulation on the floor behind the knee walls. This is used for storage and has a wood floor. Wouldn't picture 2 be better?"

Answer: Picture two is fine as long as you realize that you will now be heating the areas behind the knee walls. When you insulate, the general idea is to wrap the living spaces with insulation. Again be sure to maintain 1" ventilation under the entire roof deck.

Question: Will I trap moisture behind the foam?

Thu, 08 May 2008 16:35:04 -0500

Trip writes from West Hurley, New York: "If I add rigid foam to outside of kneewall behind our upstairs bedrooms, with existing fiberglass batt insulation with kraft paper facing in, will I create any moisture problems by trapping moisture behind the foam? Any other consideration I should account for?"

Answer: FOAMULAR® extruded foam insulation is not a vapor retarder. It is considered breathable. It has a closed-cell construction that does not let liquid water through but it will allow water vapor to pass through. If the back side of the knee wall is exposed to living space it would need to be covered with drywall. But it doesn't sound like it is so there are no other considerations.

Question: Should we leave an air space above?

Thu, 08 May 2008 16:30:50 -0500

Lynne writes again from Clinton, Ohio and sends a drawing: "Here is what the room looks like in comparison to the roof. There are knee walls with storage areas behind them."

Answer: A minimum of R-38 is recommended in the ceiling of the room you are insulating, with R-13 on the knee walls. Install more R-38 on the floor behind the knee walls. Be sure to maintain at least one inch of airflow along the entire roof line. The ceilings behind the knee walls do not need to be insulated.

Question: Can I install a radiant barrier with insulation?

Wed, 07 May 2008 06:30:23 -0500

James writes from Round Rock, Texas: "I am finishing a small attic space (not the "main" attic. I have 2x6 rafters and want to get as much insulation as possible without having to build them out. My question is as follows: Can I install a radiant barrier directly to the roof decking between the rafters, then install R19 and then install foam board over that before adding the sheetrock. Will there be enough space for air flow? Does the radiant barrier have any impact?"

Answer: Fiberglas™ R-19 insulation is 6-1/4" and will fill that 5-1/2" cavity and more. There will be no space for the recommended 1" airspace under the roof deck. Owens Corning does not manufacture radiant barriers, and has no recommendations related to their use. You may want to contact a company that produces them to find out more about their use.

Question: Is there a facing to place over the new insulation so it doesn't get in my hair?

Wed, 07 May 2008 06:24:17 -0500

Nachum writes from Elmer, New Jersey: "Paper faced Insulation in the attic was installed about 1940. IT is falling down and I want to put new insulation over the old. Your information advises to use unfaced insulation and run it perpendicular to the existing. The attic has low head clearance and our head will rub against the new material. I prefer not to remove the old stuff. Is there a recommended facing to place over the new so it doesn't get in my hair?"

Answer: Hmmm. If your attic is unfinished and not conditioned (heated and/or cooled), the insulation should be on the floor and not overhead. In such an attic there should also be ventilation to help remove any moist air that enters the attic and keep the roof deck dry. When we recommend adding new insulation in a perpendicular direction, we are expecting it will go on the floor. If the attic space is conditioned, the insulation can go overhead if there is ventilation between the insulation and the roof deck. In this case the insulation should have a vapor retarder and it should be on the warm-in-winter side, which in your case would be the inside of the attic. And if that’s the case, the Kraft paper facing needs to be covered with a 15-minute thermal barrier such as drywall. If you want to discuss your situation to fully understand our recommendations, call the helpful Owens Corning customer service folks at 1-800-GET-PINK (438 7465).

Question: What is the best way to insulate the unfinished ceiling of my garage?

Tue, 06 May 2008 06:48:15 -0500

Jeff writes from Windsor, Wisconsin: "What is the best way to insulate the unfinished ceiling of my garage that is attached to my house? The garage walls are insulated and drywalled. I use the attic area of my garage for storage and have access by means of a drop down ladder. Can I use faced insulation stapled between the ceiling joists?"

Answer: You may not need insulation in the garage ceiling if both the garage and the space above it are not conditioned (heated and/or cooled). Thermal insulation will be helpful if there is living space above the garage but you say that space is only used for storage. For storage areas above garages there is typically ventilation and insulation in any walls that are shared with the living space of the home. Insulating the ceiling and walls of an un-conditioned garage can create a "hot box" situation where daytime and vehicle heat are retained in the summer and not allowed to dissipate.

Question: How should I install insulation in the basement?

Tue, 06 May 2008 06:44:55 -0500

Shenika writes from Philadelphia, Pennsylvania: "I wanna do a back basement room it has a lot of paneling missing and the walls are cement and it's freezing cold in that room do I have to put the insulation up over the cement wall and if there are big plumbing pipes do I cover them as well or cut around them and then do I secure the insulation with nails then put up the dry wall over it and can I paint the dry wall? As you can tell this is my first time doing this but I just wanna be sure especially about the insulation because my bedroom is also located in the basement near this room."

Answer: What you describe seems good. You don't mention what you will be framing with. Will it be wood? The best thing would be to insulate the pipes first and then insulate between the studs with fiberglass. Use faced insulation if you are insulating exterior walls. The paper goes toward the warm-in-winter side, which is the interior side. The studs can then be covered with drywall and painted. Moisture-resistant nails or staples should be used to secure the insulation.

Question: Should we apply insulation at the entire roof eave to peak or over the ceiling leaving an air space above?

Mon, 05 May 2008 16:59:40 -0500

Lynne writes from Clinton, Ohio: "I have a 1939 cape cod style home in Ohio. We are in the middle of removing all of the drywall and old insulation from the attic/upstairs and plan to convert the space into a bedroom and bathroom. We plan to spray on Sherwin Williams eBarrier reflective paint on the underside of the wood roof then leave 2 inches of space then reinstall insulation underneath with the vapor barrier facing the room. I read that we should install R-33. How thick is that? I was wondering if we would have to fur out the rafters. Should we apply insulation at the entire roof eave to peak or over the ceiling leaving an air space above with ventilation? The structure has knee walls and a ceiling. I was thinking that an unheated space above the ceiling would connect with the space between the roof and insulation so that air could circulate. No one seems to have the same idea about the correct way to insulate this attic! I can email a sketch if I haven't made myself understood."

Answer: Please email your drawing to be sure so we are on the same page. Owens Corning does not manufacture fiberglass insulation in R-33. The company makes an R-38 product that is 12 inches thick. That is the highest insulation R-value the company makes.

Question: Can I put insulation on the plywood flooring?

Mon, 05 May 2008 16:56:55 -0500

Frank writes from Woodstock, Illinois: "I want to increase the insulation in my attic to meet US government EnergyStar recommended R-values. I currently have fiberglass batts between the joists. A makeshift floor of 1/4" plywood has been overlaid and secured to the joists in some sections of the attic in order to facilitate movement and storage. When adding new fiberglass batts, do I need to remove the plywood "flooring" or can I lay the new insulation directly atop the plywood?"

Answer: If the insulation fills the joist, then unfaced insulation can be placed on top of the plywood flooring. If not, the new insulation will not be as effective.

Question: What could be causing the temperature difference?

Sat, 03 May 2008 01:55:32 -0500

Richard writes from Matthews, North Carolina: "I measured the indoor temperature inside my house at ceiling height and at the floor level and came up with a temperature differential of approx 6 degrees F. I believe that my attic insulation is adequate. There is old R-11 insulation under the floor in the crawl space that has a paper vapor barrier on the side facing the floor and a thin clear plastic covering on the side facing the crawl space. It is sagging badly and needs to be re-supported. Could this be the cause of the temperature difference? Should I replace it or just supplement the existing with additional unfaced insulation? What R-value should I use in either case? Should I use batts or continuous strips?"

Answer: Yes, sagging insulation could be the cause of heat loss through the floor. The U.S. Department of Energy recommends a minimum of R-19 be used under a floor. Unfaced insulation can be added to what is there. But if there is plastic attached to the bottom of the floor joist, remove it and use it to cover the floor if it is dirt. Putting it under the insulation may cause moisture issues.

Question: Will I have a moisture issue due to a lack of ventilation?

Sat, 03 May 2008 01:52:45 -0500

Bob writes again from Sunnyvale, California: "I knew the R-values were cumulative, but I was concerned about the moisture issue. Sunnyvale CA is not a very humid area, and I didn't know if having only a 1/4 inch gap between the insulation and the plywood attic floor would cause moisture issues due to a lack of ventilation. Based on your response, you think the moisture issue will be OK if the 2nd R-15 layer is unfaced. Is this correct?

Given that 2 R-15 layers is only 7 inches thick, why doesn't Owens Corning put out an R-30 insulation product that is only 7 inches thick? Standard R-30 is 9.5 inches thick and R-30c is 8.25 inches thick."

Answer: Yes, unfaced insulation is what we recommend. Regarding your second question, Fiberglas™ R-15 insulation is a higher-density product made for 2x4 walls where space is limited. It is a more expensive product to make. Standard R-30 insulation is generally used in unfinished attics where space is not restricted. R-30c is made for cathedral ceilings where some space limitations exist. Bottom line: deciding what thicknesses and R-values to make comes after weighing a variety of factors including what the market needs, wants and is willing to pay for.

Question: Should I remove the facing where it contacts the top plate and trusses?

Thu, 01 May 2008 16:37:38 -0500

David writes from Highland, Michigan: "I just insulated my addition, R38 in the ceiling, inside pitch 2.5/12 outside pitch 5/12 with a 2" spacer for insulation space. I have the attic baffles. I pushed the insulation to the outer edge of the wall's top plate. Where the Kraft paper contacts the top plate and trusses, it does not sit nicely due to the slight bend. Cold air easily comes through at the corners. I'm thinking about removing the paper where it contacts the top plate and trusses so insul can expand into the corners. Maybe remove the paper an inch from the inside wall surface. See any issues? I should not need the paper on top of the wall, outside of the interior air space."

Answer: I see no issue with that if the vapor retarder covers the ceiling below.

Question: What should I do if the attic already has faced insulation?

Thu, 01 May 2008 16:33:55 -0500

Bruce writes from Pine Plains, New York: "I purchased R38 $500.00 of faced insulation from Lowe's in Kingston New York, the contractor tech in the store advised me it was OK to use the faced insulation on top of the beams and insulation that was there already. This did not seam correct but he stated that was OK to do. After I started this project I felt this was wrong! I search for information and found in Owens Corning energy saving paper work it states…. (USE UNFACED OVER ADDING TO EXISTING INSULATION IN THE ATTIC). What do I do NOW?????"

Answer: As you accurately noted, when insulating on top of existing insulation we recommend using unfaced insulation so no vapor retarder will be on top of the original insulation. However, insulation with a vapor retarder can be placed up to one-third of the total thermal resistance in the assembly starting from the warm side. If the insulation you are adding has at least twice the R-value of the insulation already in place, then it should work. The other options are to remove the vapor retarder from the new insulation you will be placing on top of the existing insulation (messy and not really recommended) or freely slashing the new vapor retarder with a utility knife.

Question: Do you still make insulation covered with plastic?

Wed, 30 Apr 2008 16:12:36 -0500

Margie writes from Riverside, New Jersey: "Do you still make the insulation pieces that were 16 in by 24 in and covered by plastic so they were mold resistant? If so, who sells them? If not, is there any thing comparable?"

Answer: This sounds like a description of MiraFlex multi-project insulation which was discontinued several years ago. Owens Corning no longer makes fully encapsulated insulation products. A product to consider is Owens Corning PINKPLUS® insulation available at Lowe's. It is not fully encapsulated but it is faced on one side and covered with fabric on the back side.

Question: Is it dangerous for my daughter to breathe this?

Wed, 30 Apr 2008 16:09:24 -0500

Gerri writes from Freehold, New Jersey: "My husband took 2nd floor ceiling out 6 years ago, was planning to make a very tall second floor, we have a small thin hallway 6x 20 feet. with attic space on both sides on top and bedrooms on both sides 2nd flr level, my question is, 6 years ago he put up 2x4 wall to rafters on both sides of hallway. With insulation bought at home depot. It has torn and been exposed since then; it has shiny paper i think its fiberglass. My daughter's bedroom door opens up to this space she's 3 years old son is 18 is it dangerous for her to be breathing this in? Want hubby to complete this project."

Answer: I can't help with getting your husband to complete the project but I can tell you there is no long term health risk in the situation you describe. There is a possibility of irritation if the insulation is handled. That irritation is a mechanical abrasion caused by the ends of the fibers scratching the skin. This is not an allergic reaction and the itching generally subsides when the source of the irritation is removed by washing it off.

The few fibers that are small enough to become airborne and breathed into the lungs will be removed as fast as the ordinary dust we breathe every day. They simply don't stay in the body long enough to cause disease.

Based on more than 60 years of research, we believe our glass fibers are safe to manufacture and use. When working with the material we recommend following industry safe work practices to avoid irritation.