Insulation
John Connell founded the Yestermorrow Design/Build School in 1980 and the Yestermorrow Building Group Inc. (later to become 2morrow Studio in 1982.) He taught at Yale's school of architecture for five years after which he authored the book Homing Instinct: Using Your Lifestyle to Design & Build Your Own Home, McGraw Hill, 2000. Besides teaching he is currently designing green homes that tell "stories", design/building treehouses for handicapped children, and animating short films. 2morrow Studio puts into actual practice the design/build philosophy taught at the Yestermorrow School. A small design/build firm in Vermont, 2morrow Studio works with residential and small commercial clientele interested in integrated energy-efficient architecture using the latest green and sustainable methodologies. Besides architectural design, Connell is an experienced team builder, group facilitator and educational program designer. The Yestermorrow School teaches people how to plan, design, build or renovate their own homes. It is staffed by over 40 architects, builders and artisans from all over the United States who believe that the way to improve the built and natural environments is to re-involve people in vernacular architecture.
Questions and Answers
Q: My wife and I have been working on plans for a cob home we intend to build in Vermont, hopefully within the next few years, and we've been researching natural insulation. If we go with wool, is a vapor barrier needed, as wool can absorb considerable moisture before loosing insulative properties? Would a living roof provide enough insulation on it's own, or would it also need some other form of insulation?
A: Yes, wool insulation used in Vermont should definitely be installed with an eye for moisture control. Moisture, as you probably know, occurs in building assemblies (roof, wall & floor) as a result of cracks in the assembly and migration right through the materials that the assembly is made up from. My suggestion would be to use a 6mil poly air barrier on the studs, taped at all joints and caulked at all protrusions: ie. outlet boxes, vent stacks, plumbing runs, etc. Keeping the moisture laden air out of the walls will account for almost 90% of the moisture. The other 10% can be controlled with the use of moisture barrier paint. (As an alternative, I use cellulose blown into my stud spaces to the manufacturer's prescribed pressure spec. That way, I don't require a moisture barrier.)
As for your living roof, you should definitely plan on additional insulation. Earth that supports life is usually wet and has very poor insulating characteristics. Vermont is a pretty chilly place. If you're confident that there will never be any leaks (membrane or concrete roof), you might consider wool, cellulose, fiberglas, rice hulls, etc. but if there is a possibility of roof leaks (usually!), then I would suggest looking at the family of foams. They tend to do better at retaining some insulating value even when wet. Hope this helps. Let us know when you start construction so we can bring a bunch of Yestermorrow students over to help.
Q: I have just purchased a 1900's clapboard siding home in Savannah, Georgia. I have been trying to get some answers on cost effective ways to insulate without creating a moisture problem. The house has wood siding in good condition, nailed directly to the studs, balloon framing, with no sheathing or vapor barrier between the exterior sheathing and interior wall board (future). Most of the plaster has been removed on the interior and I will go back with gypsum board. Where there is plaster it will remain. I would like to insulate the walls with R-19 Batt insulation, but there is no vapor barrier. Since in the south, the vapor barrier should be on the exterior side between the siding and stud, I fear potential moisture problems if I install insulation without a vapor barrier; or if I install the vapor barrier (felt paper) to the inside. I thought I could install the felt between the studs to the exterior, with insulation behind, sealed tightly. But I feel this will not drain properly I fear and will only rot the sills as it drops to the bottom of the wall. Since there was never Central HVAC installed, I am sure moisture was never a problem. How can I keep the moisture out, fill in-between the studs with insulation without removing the siding?
A: If I were you I would line or fill the stud bays with an insulation product that is also a vapor barrier - i.e. foam. If your budget can support it and your green values tolerate it, use polyurethane foam blown in with green agents. This is a high R-value, sprayed in place, closed cell foam that will also act as a vapor barrier. It's very expensive and not all that "green" but it will be the best solution for your house. To keep the cost and environmental damage to a minimum, use only 1" on the inside of each stud bay (including the sides of each stud). Same goes for the rafters. Then fill up the rest of the bay with either icynene foam (an open cell foam of slightly lesser R-value but better "green" rating) or dens-pack cellulose. Cellulose, of course, is the most sustainable and
least expensive but in your climate it is susceptible to mold so I only suggest it with this caveat: retain only the most experienced and reliable installer. And when you find him, ask what he would do if not what I suggest above. I am a big believer in listening to the local talent when it comes to anything that has to do with moisture movement. He has
probably seen dozens of houses just like yours.
Q: I've purchased an old farmhouse in Maine, with virtually no insulation. We are trying to find the most energy efficient (and cost effective) option to add insulation. In Maine, R40 walls are recommended, but realistically we will not even approach that level. We currently have 2x4 walls, and are considering removing the sheetrock or plaster/lath (different parts of house built with each), making walls 2x6, then insulating. Or, I've read somewhere about an R7 foam which can be used to fill wall cavities, but can't find any information on it. I like this idea as it might save money and resources by not tearing out perfectly good sheetrock and plaster/lath, but am concerned about offgassing from foam, as well as toxic fumes if there were a fire, and ultimate disposability issues if the house were ever torn down. If we were to tear down the interior walls and build out the studs, I am not sure what insulation we would use - cellulose, cotton, or fiberglass (our builder likes fiberglass, but I am not convinced yet that it is the right choice). What are your thoughts on insulating an old house like this, and the different products available?
A: Indeed, you can produce a VERY tight and well insulated house using polyurethane spray-in foam. While it has approximately an R7 rating, it's incredibly expensive (around $15,000 for your house, at the very least) and it's not "environmentally enlightened", strictly speaking. The blowing agents used to install polyurethane tend to attack the ozone layer. Even when the better, greener blowing agents are used (more cost!) you're still stuck with the fact that urethane is a petroleum product and pretty ugly stuff until it's in place. However, having said all that, it's a FANTASTIC insulator, doesn't off-gas and has an incredible fire rating- I tried to ignite a blob of it once with a brazing torch and couldn't. It just smoked a little. If it's covered by drywall or plaster, I wouldn't worry about it. And if the house is ever torn down, the foam will be the least of your land fill problems.
OK so that's foam. But if it were MY house: I'd either use icynene foam (more environmentally defensible) or cellulose. Cellulose is my first choice but it will require that you restructure your walls to get a full 5.5 inches. If you're up for the effort and fun, I'd use the cellulose. You'll sleep better and so will the rest of the world!
Q: We will be insulating an addition to our house in Maine with dense pack cellulose. The walls are 10" thick, staggered studs, with Advantek sheathing and Tyvek on the outside. Our insulation contractor is suggesting that we use damp-spray cellulose. Our building contractor believes that we need a vapor barrier. I am a bit concerned about not using a vapor barrier, and also that 10" thick walls may not dry out adequately if we wet spray them. I would love to hear what an expert has to say about this!
A: It seems you already have some experts giving you opinions. Remember that your insulating contractor should warrantee his work against defect and that includes mold and rot from inadequate drying. Get it in print!
But just so you can have an expert (as defined by anyone who lives more than half and hour away) opinion, I wouldn't put a vapor barrier in this wall assembly. I would install my sheet rock using the AirTight Drywall approach and paint it with vapor retarding paint. The 10" of insulation should put the dew point way outside any possible moisture migration in the wall. Still, a lot depends on where you live. Are you on the shore or in the mountains? In Vermont the winters are so arid that any moisture migration into such a wall assembly would more than dry out during the winter. But if you live on the coast where it's high humidity all year round, it might be different story. In that case I'd heat my house with wood in order to dry it out in the winter. Either way, I put more faith in the moisture coming back out than I do in a vapor barrier keeping it out in the first place. So use the 10" of damp-spray cellulose, leave the walls open for at least two weeks (longer if possible), forget the vapor barrier and maintain low humidity within the house for a major portion of the year. That's my advice.
Q: We have a 400 year old stone house in the Cotswolds, England. We are trying to insulate the windows to conserve energy. We aren't allowed to put in storm windows because the local heritage control agents won't give us permission (our house is a listed building of architectural/historical importance). I'm using blinds and heavy curtains. In the bedroom we have terrible condensation on the (leaded) windows which the insulation of course makes worse. We can't have wood burners in the bedrooms-too dangerous (Carbon Monoxide risk). Any ideas for sustainable dehumidification?
A: The humidity really shouldn't be let go below 40% and at that level you will still get condensation on your windows if they aren't insulated. So how about interior storm windows? If you can have a local carpenter frame some insulating glass in a nice frame, that will do the most for reducing condensation and reducing energy use. But keep in mind that the interior storm windows must be air tight or the moisture laden air will simply leak around it and freeze on the window beyond. I don't think dehumidification is the answer.
Q: We have to apply to the Council for Listed Building Consent every time we try to do anything substantial, and we applied last year to put in temporary glazing and were turned down on the grounds that it would spoil the appearance of the insides of the windows ! I have rigged blinds made of rubberized cotton between the windows and our heavy lined curtains. The condensation remains bad and there is heavy mildew even with monthly attempts at spraying. We would try a dehumidifier powered by a solar panel but the local council have let it be known that they are opposed to any solar panels anywhere on listed buildings.
A: I'm thinking you will never get rid of the bedroom humidity without moving air (sleeping humans are a relentless source of humidity). So, this can be done either with electricity or thermo-active gravity effect (hot air rising, cold air sinking). Since the use of electricity defeats the purpose, we need to see if there is a way of circulating the bedroom air with the drier downstairs air (heated by stoves). I really can't advise in any detail without a set of drawings. Nevertheless, if the floors are wood and there is space for a few registers, this may be half the battle. To get the hot dry air to rise into the bedrooms we need to suck the humid air down and out of the bedrooms (or up and out, but that uses more energy). To evacuate the humid air it will need to be drawn down by the force of the hot air rising (somewhere else). This is a delicate balancing act which requires sizing of apertures and whatnot. Still, it's entirely possible if you can find someone with the experience in forced air systems. I'm sorry if this is all about as clear as mud. It's just so hard to solve this kind of a problem "in general". Send me some plans or a plane ticket and we'll have it worked out in a jiffy.
Q: I have also been recommended to seal the windows with silicone rubber but having worked with this material in another context I am suspicious of the long-term effect of the solvents in this material on the oolitic limestone which is the material of which the window frames are made.
A: (Kelly) It is my understanding that once the silicone sets up (usually within about an hour) it becomes rather inert and is not likely to negatively affect the stone. Sealing all points of draft within the shell of your home will be essential to control the humidity and to make your home comfortable.
Q: How to, or what product to use in insulating underneath a home built in 1926. I live in Los Angeles, CA. The floors are brand new, so I do not want to rip them out...but they get cold in the winter..what should/could I use as insulation on the underneath (crawl space?) to insulate the house? I already put a .9ml black plastic there..but we are still cold.
A: Indeed, your issue is quite straight forward. Assuming you have adequate space to maneuver, here's what I suggest: Place the .9ml plastic on the ground and, if possible, weight it down with an inch or so of sand. This will prevent moisture from coming up from the ground that might rot your framing (over a long period of time). But the plastic will do nothing for your heat retention. Spray a polyurethane foam in all the joist bays to a thickness of at least 2"....more if you can afford it. The rest of the joist bay may be filled with inexpensive fiberglass. Cover the underside with a nonflammable material like FR gypsum board, Jamie Hardie panels or similar. (Fire code) Guaranteed you will be toasty!
A cheaper but more labor intensive approach would be to cut and fit rigid 2" blue-board into all the joist bays and then foam the edges with hand held foam product or a small "froth pack". Let me know if this doesn't make sense.
Q: I am building a new home in Wasilla, Alaska. It will have 6 inch interior walls with batted insulation and a visqueen vapor barrier, then sheetrock. I am considering putting R-tech insulation on the exterior of the house to provide a better insulation R factor. Will the R-tech on the exterior create a double vapor barrier? The house size is 4800 square feet.
A: I never use fiberglas insulation anymore and I only live in Vemont - not Alaska. In particular, I would never use batts in any place colder or more humid. If you must, then the rigid insulation on the outside is imperative. Make it at least 2" thick and tape all the joints. Ideally, you should spray at least 1" of foam (cymene or polyurethane) on the interior between the studs as well. This will give you a tight house but, more importantly, it will place your dew point far enough toward the inside of the wall assembly so condensation will be unlikely. Then, omit the interior visqueen altogether. This will only trap the moisture that will inevitably penetrate the walls. Let the walls breath to the interior and make sure you control humidity with either an air-to-air exchanger or an AC unit (which will be hard to find in Alaska!)
Q: I am building a workshop and have used traditional building construction methods. The framing is done, and the roof is completed. I am using OSB for the outside walls with building wrap, then covering it with metal siding. The roof is plywood with 30lb felt paper with a metal roof covering. I would like to use a loose straw mix for wall insulation. I like the idea of packing the wall cavity with the straw mix. The outside wall is already formed, and I plan to use plywood on the interior walls, this will serve as the forms. In your text you stated that the mix should not touch the metal directly. The building wrap should allow The building to breathe. Do you have any suggestions. I live in North TX due to high winds and storms. I would prefer to use the metal.
A: I've never been a big fan of packing walls with organic material unless I'm absolutely certain of its moisture content and it's bug content. It sounds like you're planning on forming up walls with a straw cement (clay?) mix. That's fine if you strip off the forms from at least one side after the pour. Otherwise there will be rot and mold for sure. How fast they develop depends on what part of Texas you're building in and what the local climate is.
Q: I am building a house with insulation in wood shaving. It seems that I have to add Borax or lime for resistance of bug and fire. Is Borax better then lime? Do you know what is the percentage in volume that I have to add?
A: (Rob Roy) We mix in one part of lime with 12 parts of sawdust to make our insulation. The lime helps against insects, and I'm sure the Borax would, too. Another benefit of the lime is that if the sawdust gets wet during construction for any reason, the lime will set up with the sawdust, yielding a kind of beadboard product. If it stays dry, it remains like a loose fill insulation. I don't know if either Borax or lime will do anything about fire-proofing wood shavings. We avoid wood shavings in cordwood masonry because it is so hard to place between the mortar joints. We have used it when there has been nothing else, usually at regional workshops, but much prefer sawdust.
Q: I am living in a 1132 sq. foot home built in the 1920's. The house sits on 8 by 16 inch blocks and they are stacked two high all around the edge of the house. The opening is 2 blocks high and one block wide. There is no subfloor the wooden floor is nailed directly to the floor joists. The home has forced air heat. this winter the floor was very cold while the knee high areas of the home were comfortable. I am having trouble finding anyone that will go under the house and install batting for insulation. Is there a way to insulate the crawl space or outside of the crawl space to reduce the cold air coming up from under the house in the winter. Can I berm around the blocks creating the walls of the crawl space and leave the vents accessible but with better winter insulation when they are closed? I was thinking of raised beds after putting in protection between the base cinder blocks and the dirt in the beds.
A (Kelly) My advice is to at least insulate the foundation on the outside, and possibly down some distance into the ground, to buffer the cold from entering the space under the house. This could be done with commercial insulation panels that are designed to be buried. Then you wound need to protect this insulation, and this could be done with berming up against it or with some other more durable material, like bricks, rocks, stucco, etc.
Q: I live in Bali and I am building on the seaside in a quite hot and dry area. We have a lot of lava stones on the land and I would like to use them for the walls. but I am not sure about the insulation and sound proof qualities. My idea is to build the outside from the rocks and the inside of the wall with mud bricks. But then I think that the concrete for the rock wall destroys the good qualities of the mud wall. I want to have really good thick walls as heat insulation.
A: (Kelly) If the lava stone is light weight and rather airy, then it should provide fairly good insulation. I once built a very well insulated house with crushed volcanic stone put into earthbags to build the walls. Using mud bricks on the inside is also a good idea, since these will help stabilize the interior temperature, and absorb any extra humidity you might experience on the seaside.
The only concern I have is that they use so much cement for building those stone walls. I was thinking to use mud mortar for it, but then it is maybe not so stable in this climate and its also an earthquake zone...but I am building a round room with the stone/earth wall under a big roof so stability should be good for the wall.
Many rock walls have been built using mud for mortar, and this can work if there is enough clay in the mud to make it sticky, but not so much that it shrinks when it dries. About 1/3 clay and 2/3 sand is good. You can't expect mud to last as long as cement over time, which is why cement is usually used. You can mix about half lime with the cement mortar, and this reduces expense and makes it more ecological and also improves the stickiness of the mortar.
Q: I am remodeling an abandoned plaster and lath house that is mostly down to the lath and has no insulation. Any tips on how to best insulate vertically in cold temps (Detroit) would be appreciated.
A: (Kelly) For insulating the walls, one of the best, and most ecological choices is blown in cellulose, after the walls are finished.
Q: What's the best way to insulate a timber framed garage converting to a living space? I'm in the high desert near Joshua tree national park - hot summers cold winters occasional frost. Sand is readily available! Can it be used somehow or would something like cellulose be the best option?
A: (Kelly) Sand won't provide much insulation, but it can be used as thermal mass to help moderate interior temperatures if you place it in earthbags and build something useful with it. For insulation, you are better off with cellulose (if there is a cavity or void to hold it), straw, or other conventional insulation products.
Q: I was wondering if there is a natural insulation material that could be put under a modular home?
A: (Kelly) There are a number of natural insulation products that could be placed under a modular home, including sheep's wool, cotton fiber, soy-based foam, cellulose fiber.
Which is the lowest cost? Is there anything that could be DIY?
I would suggest shopping for the cotton fiber batts; they are sold commercially, are made from recycled jeans, and can be installed by someone willing to go under the home with a staple gun.
Q: We live in a home we put together 20 yrs ago, and want to improve on it. I say 'put together' because that is a good description. We took 3 older mobile homes & put together, joining walls, remodeling inside & out til we had a triple wide home. We put one new roof over all & put vinyl siding around. We are very pleased with this, except for trying to heat in the winter; it's very hard to heat.
We have decided we want to retrofit our existing home with earthbags to insulate from the outside. I know it will make our home much warmer, but we are not sure how to work around existing Windows & doors.
A: (Kelly) You could do what you describe, but I'm not sure that you would get the results that you want, especially if you fill the bags with soil, which would not provide very much insulation. A better fill material would be something insulating, like crushed volcanic stone, pumice, perlite, or even rice hulls. Chances are you would need to extend your existing roof to cover the additional bag walls, create some sort of foundation for the bags, as well as deal with all of the details of casing around window openings, etc. All of this is a lot of work and expense.
If I were doing this, I would look into the possibility of removing your vinyl siding and installing some fairly thin insulation panels that only take up a few inches, and then replace the vinyl siding. Or another possibility is to have the house sprayed with foam insulation before reinstalling your siding. Then your roof could likely remain as it is and the window and door details would be much simpler to accomplish.
