I think it’s time for me to introduce my readers to one of the most important concepts of building eco friendly homes. House as a System.What do I mean when I say your house is a system? It is a combination of inter-dependent parts that make up a whole building. As an energy professional and an architect, that means, if I chose to change one part, I am affecting other parts of the system. This may be in a good way, or it may be in a harmful way. With the emergence of building tight homes, we also need to be aware of what we are trapping inside that previously exited though drafty or leaky areas in the home. I was going to write “older homes”, but my experience as an energy auditor has taught me that it has little to do with the age of the home. There are just as many leaky, drafty, inefficient new homes as there are older homes.It is extremely important today to understand the impacts of building more efficient homes. This rule applies to architects, builders, and energy professionals. The chemicals found in our building materials can be very harmful to your health. Many products are made with formaldehyde or high volatile organic compounds (VOC’s). Maine also has high levels of radon due to the rocky ledge that makes up our soils. By building tighter homes, we must be sure we are not trapping harmful gases or compounds within the home.Building tighter homes isn’t just about air sealing with caulks and spray foams. Adding dense packed cellulose to your walls increases the insulation value of your home, but it also reduces the air infiltration. When we reduce the air infiltration we can cause our atmospherically drafting heating appliance to blow exhaust fumes back into the home instead of out through the chimney. We can trap moisture within the home, propagating mold growth and moisture damage. Many building professionals believe that houses needed to breath and that is simply untrue. Houses do not need to breath, the occupants do. And we need to be sure that the air our homeowners are breathing is both healthy and adequate.Houses that breathe draw in outdoor air from anywhere there is a hole or crack in the building structure. This often times means that air is coming in from your basement. When you think about the principle that hot air rises, you can imagine the cool air being drawn in from your basement and leaking the heated air out through your attic. Now if you think about your basement, you may be thinking about a dirt floor, all the chemicals you store there, or your heating system. All that air that is being drawn in through your basement is introducing those chemicals into your living space. We have a tendency to think of our basements as outside of our living space, but they are very much connected to every other part of your home. Although the things you store there may be out of sight, out of mind, they are definitely not out of the air you breath.Before the emergence of energy efficient and airtight building, homes were able to dry out due to the air movement through the structure and the lack of insulation in the walls. The homes would dry during the wet seasons of the spring and fall, however, these same homes would become very difficult and expensive to heat during the winter. The energy community knew they needed to button up the homes, but at the time, they did not know that they needed to provide mechanical ventilation for healthy indoor air quality and they created several sick buildings.Now we talk about passive house building where there are less then 15 quarter-size gaps, cracks, or holes in a building structure and the sun heats the home virtually eliminating the need for a heating system. These inter-dependent parts create a very efficient design. In passive house standards, it extremely important to provide mechanical ventilation to the space. Providing fresh outdoor air to the occupants of the home eliminates harmful byproducts from the construction materials and excess moisture from cooking, breathing, and showering. Because the home itself has very little air infiltration, mechanical ventilation is often provided by a heat recovery ventilator or energy recovery ventilator. This allows the system to provide fresh air directly to the locations of the home that need it, like the bedroom, where you spend most of your time while you are at home. Providing air directly to the locations where it is needed instead of drawing it in from wherever there are cracks in the foundation allows for the system to perform with precise calculations and reduces any loss associated with providing healthy indoor air quality.The increased levels of insulation from the code minimum help to keep heat within the building envelope. Large south-facing windows can take advantage of the sun and heat the home through heating thermal mass, often a concrete floor. All parts of that system have to work precisely together to make the house as efficient as possible. If a new homeowner came in and decided to throw a carpet over the concrete floor they would reverse the effects of the solar heating system and require a larger heating system to be installed. Tighter homes often do not have large gas cook stoves with 300 to 600 CFM ventilation hoods because there is simply not enough air infiltration to provide adequate supply to the ventilation system. Without that adequate air it causes the ventilation system to “suck” on the house and will quickly burn out the motor in the fan.These are just a few examples of how the components of your home work as a system. So as you are building your home and thinking about making something that is more efficient, make sure you consider hiring a professional who can provide you with the information you need to save money, but also provide you with a safe and comfortable home. It may sound daunting to build an energy efficient home, but the comfort level it can provide you and the energy it can save you is well worth the added considerations during the design or renovation process.
While I was teaching the last couple of days, several issues came up and one of them was fiberglass insulation. I tell my students at the beginning of the semester that I hate fiberglass insulation and very rarely use it, but that’s not really fair or true. Used in the right context, fiberglass insulation can be just fine. However, I find all too often that fiberglass is used in the wrong way. It really is not great as wall or attic insulation and it’s often found in basement ceilings where it’s installed up side down. So I thought it would be good to discuss when and where to use fiberglass insulation, and why it doesn’t work in all locations.First, fiberglass insulation works by trapping the air in between the fiberglass fibers. So fiberglass insulation is really only effective when there is absolutely no air movement where it is installed. Air movement through the insulation removes those trapped pockets of air and essentially makes it a filter. And no matter how tight you build a building, you are still going to have air leakage in some areas. That’s why; when you pull it out of the box sill in your basement it looks black. That’s just the air infiltration from the box sill being filtered through your insulation and making it useless, since it is no longer trapping air pockets within its web of fibers.The box sill or band joist, is often one of the leakiest locations in a home, and therefore one of the worst places to install fiberglass insulation. Fiberglass insulation rarely works well in the wall cavity because your siding breathes and tongue and grove wall surfaces are not airtight. Wall cavities can also be open to the box sill below. If you follow the principle that hot air rises, then that air is always going to be traveling up through your wall cavities, taking warm air with it, and cooling off the sheetrock on the inside. It also performs poorly in the attic due to wind washing. Wind washing is the effect that happens when the air enters your attic through your soffit venting and blows through the insulation. Contractors install proper vents to try to direct the air above the insulation. But I have been in many homes that have improperly sized or installed proper vents, or none at all. Not installing the proper vents and insulation dam causes the wind to be pulled through the fiberglass insulation, again releasing the trapped air molecules in the fiberglass and making the insulation less effective.If you have a heating system, plumbing, or laundry in your basement then the insulation does not belong in your basement ceiling. People argue with me all the time that they do that just to make the floors warmer; well that’s not a good enough reason. You’ll be thanking me when you don’t have frozen pipes and the excess heat from your boiler can rise to the floors above. If you have any of the things I mentioned in your basement then the thermal boundary of your space is the wall. If you have rubble stone or granite the best wall insulation is spray foam. If you have smooth concrete then the best insulation is rigid insulation. If you live in Maine the rigid insulation needs to be Thermax insulation approved by the Maine State Fire Marshal’s office for use without covering. Otherwise, you have to cover your rigid insulation with a 15 minute thermal barrier – which is 1/2” Sheetrock or ¾” OSB. You are also required to cover your spray foam insulation with a thermal barrier that any spray foam installer can spray on as part of the insulation process.But I digress, we were talking about fiberglass, and why it seems to always be installed in the wrong place or the wrong way. The Kraft paper side of the fiberglass always needs to be to the warm side of the structure. So in Maine, it needs to face to the inside. Fiberglass is only as good as it is installed. The Kraft paper should be face stapled to the studs, not side stapled which compresses the insulation. The fiberglass insulation should be cut and fit around electrical wiring so that it is not compressed behind the wire. And it needs to fit fully into the cavity, touching both sides of the studs, as well as, the top and bottom. All too often insulation is installed by the lowest paid guy on the job site. It’s one of the most critical pieces to get right, but it’s nasty work and therefore done by the new guy. In basements, the Kraft paper side needs to be up against the warm floor above, not stapled to the floor joists below– I know this is easier to install, but it’s putting the vapor barrier on the wrong side. And in the North East we strap our ceilings, which makes fiberglass insulation the worst type of insulation to use in your attic. The ¾” strapping leaves a ¾” gap between the ceiling sheetrock and the insulation above allowing air to carry the heat away from the sheetrock without the protection of the insulation. That moving air also reduces the effectiveness of the insulation above. So make sure that your insulation is in full contact with your sheetrock ceiling. The proper way to solve this problem without adding a lot of extra expense is to pick up your fiberglass insulation, blow in 3 inches of cellulose, cut the vapor barrier on your existing fiberglass insulation and lay it back down on top of the cellulose. If you need more insulation to meet the code minimum, blow an additional couple of inches of cellulose over the top of your fiberglass insulation to make a fiberglass sandwich. The density of the cellulose minimizes the airflow through the insulation and makes the fiberglass more effective.Where would I use fiberglass? Well it makes a great sound barrier, so I would use it around the master bedroom and around bathrooms to reduce noise levels. I would also use fiberglass insulation in conjunction with rigid insulation in basements if you were going to finish a basement, because it does not hold water, and basements can be moist. It has its place, in a completely sealed envelope it can add a lot of r-value to a system, but it needs to be installed correctly and in the right location.
As of September 15th it's heating season again. If you live in New England, or more specifically, Maine, then you know that means it's time to fill your tank with Fuel Oil again. It's a sad reality for me, that Natural Gas lines are less then .25 miles down the street, but just out of my reach. Our street was paved last year, and city ordinances require that you can not rip up the pavement for a certain number of years.I knew the city was going to pave our street, so prior to paving, I reached out to the natural gas company in our area. I was told that I would need to petition my neighbors and convince several of them on our street to switch to natural gas. If you are a homeowner or building owner, you know that replacing your heating system is a costly upgrade and very few people are willing to do so. Sure i'm an Energy Consultant and I could have run the numbers for all of my neighbors on the savings and payback for moving to natural gas - but let's be honest, who has that kind of time!So instead I leave you with a few nuggets of wisdom that I use when I do all of my residential energy audits.1. Have an Energy Audit done on your home. A great energy auditor is trained to understand your home as a system and figure out where air leaks are coming from and what the best solution for your individual home is. Even homes built from the exact same plans will be totally different, so make sure you hire the right energy auditor, that will give you an assessment on your unique home.2. Air sealing is the cheapest and nets you the most savings for the dollars you put in. Everyone has heard the term "hot air rises" so start in your attic - seal around anything that protrudes through your ceiling and into your attic space. Grab a tube of caulking and a can of 1-part spray foam from your local hardware store and make that first adventure into your attic. Air sealing isn't rocket science - but be very careful to stand on the joists and not fall through the ceiling. If you're not agile, or willing to climb around in your attic on a saturday afternoon there are plenty of hungry contractors out there willing to do the job!3. Add insulation - adding insulation to your attic is the best place to start because it is usually easy to get to. If you haven't done the air sealing mentioned in number 2, don't even bother with the insulation - you'll just be wasting your money.3. After you've done all the insulation and air sealing - then consider upgrading your heating system. You ask - why do I leave this for last - I have an old heating system and it will save me the money I need to add the air sealing and insulation. Well that might be true, but once you add the air sealing and insulation, your heating system will be oversized and you'll lose money from short cycling.So this heating season - as the leaves begin to fall and we start thinking about winter again - keep in mind - that a good energy audit can tell you a lot about your home, and save you money all year long.