The Energy Efficient Home

Energy Star Home Certification

I started thinking about making our living space more energy efficient back when I was in college, when I did some volunteer work at a place called Urban Options in East Lansing (now called Michigan Energy Optionslink opens a new window). We only had an apartment in a drafty old Victorian house, but I was still into "green living" well before it was trendy, I guess. When I later moved to a rental house, I did what I could with caulk, insulation, set-back thermostats and such to try and reduce our energy costs (and save money of course). Now that we own a home and are renovating everything in the house, I can finally take some significant steps to improve our homes energy efficiency as I rebuild the entire structure and install new appliances and mechanical equipment. Back in the college days, there really wasn't a definitive answer to what making an energy efficient home actually meant - you just did what you could to stop air leaks and use more efficient heating and cooling practices. Now we've got a much better definition of what an energy efficient home really is.

The good news is, "green building" and "energy efficient home" building techniques are very popular these days, so there's plenty of information available on both subjects, mostly through the Environmental Protection Agency's Energy Starlink opens a new window program web site. Energy Star also has a complete verification list of the specifics to determine if the entire home is Energy Star qualified, so there's no more guessing about what works and what doesn't.

click to magnify At least it's not a negative number.

The bad news is that while I'm taking as many steps as I can to improve our homes efficiency, it's a slow process and the home is performing horribly at the moment. One of the ways to measure our homes energy efficiency is to use the Energy Star Home Energy Yardsticklink opens a new window which provides a rating based on the energy usage data provided and cross-referenced against heating and cooling degree days for the time period in question. On a scale of 1 to 10 (10 being the best), we scored a whopping .5. Sad, but it makes sense given that much of our house remains uninsulated while renovations are being completed.

Unfortunately, there doesn't appear to be a way to make an existing home an Energy Star qualified home under the current guide lines. Qualification only applies to new construction, so despite the fact that I'm essentially re-building every component of the home, I cannot create a true Energy Star qualified home according to the EPA. Even though I'll never get an "official blue sticker" for my electrical panel, there's still nothing that prevents me from going through all of the Energy Star qualification check lists and doing everything right. Even without the sticker, we can still enjoy the benefits of lower energy costs and reduced environmental impact of an Energy Star qualified home. And I haven't given up on that sticker yet either... I'm working with the EPA and an Energy Star rater to determine if I can still receive the appropriate verifications to qualify for the program even though I'm doing all the work myself.

Reducing energy use costs for our house is the main goal of improving the homes energy efficiency, but that means we must do a lot more than just concentrate on weatherization. In order to enjoy a comfortable living space with a minimal ongoing energy budget, we need to address the entire building as a working system. Weatherization is certainly a big part of improving the energy efficiency of the structure, however the additional factors of Indoor Air Quality (IAQ), building moisture and mold prevention, and combustion safety are no less important. Throughout the renovation project, it's been necessary to ensure these factors have always been in mind while making improvements to the building. A little caulk around the windows and a few rolls of fiberglass insulation in the attic when it's all done isn't going to do the job.


Improving Energy Efficiency

Creating a Thermal Barrier
Perhaps one of the most important and cost effective steps in improving heating and cooling efficiency is to prevent air leaks in to and out of the conditioned space. We're paying to heat (or cool) the air inside the home, and the greater the temperature difference between in the air inside the building and the air outside the building, the greater the stack-effect forces driving convective losses through air leaks. The air in the building is warmed by the homes heating system (radiant floor heat in our case), which then makes the air less dense so it wants to rise. In order for the light, warm air to rise and escape through air leaks in the attic, cool, dense air tries to enter the structure through air leaks in the foundation or window and door openings (making the home feel "drafty"). The same thing happens in reverse when cooling the home, in that warm air is drawn in through the attic to replace cool air that's lost through the foundations. If the air leaks are stopped, the stack-effect can be minimized.

Fiberglass insulation, which is what we're using the walls and attic, does nothing to stop air movement - insulation prevents conductive heating and cooling loss, not convective interchanges. In order to stop air leaks we created a sealed envelope between the conditioned space inside the building as the first layer of the thermal barrier, followed by the insulation, then another sealed envelope / moisture barrier outside the building, just below the "weather shell", as the outer layer of the thermal barrier.

Sealing Air Leaks
Because we've been gutting each room to the studs to gain access for new wiring and plumbing as we work through the interior renovation, the process of sealing the interior is relatively straight forward. Once any electrical boxes, wiring and plumbing is in the wall, the next step is to seal any penetrations in the top and bottom plates of the wall with expanding spray foam. Rather than use throw-away cans of Great Stuff™, which pretty much need to be emptied once they're started, I use a Todal Products® link opens a new window Pur Shooter gun and their Pur Fill 1G foam for air sealing any large gaps (see the HVAC section regarding under-floor insulation for more information on the foam gun kit).

Once the big penetrations are sealed with foam, I also go around the perimeter of any electrical boxes with the foam gun, sealing the wiring openings and filling the space between the back of the box and the outer wall sheathing with foam. If the wall has a window in it, I then seal the small gap between the window and the rough opening framing with DAPTex® link opens a new window Latex Multi-Purpose Insulating Foam Sealant. While DAPTex® is in an aerosol can, the nozzle can be removed and cleaned with soap and water between uses so the stuff has a good shelf life. It also doesn't expand like crazy the way polyurethane foam does, so there's no possibility of distorting the window or door casing after it expands.

click to magnify Sealing plumbing and wiring.

Next the wall cavities are filled with unfaced fiberglass insulation (see below), then the entire surface is covered with 4-mil polyethylene plastic sheeting as a vapor barrier. Before installing the poly, I go around the perimeter of the wall (top plate, bottom plate, corner studs, window openings and electrical boxes) with a nice heavy bead of Tremco® link opens a new windowAcoustical Sealant, which is a non-hardening, non-skinning synthetic rubber caulk. The stuff is the nastiest, stickiest mess to ever come out of a caulk gun, but it works. I used "regular" acrylic latex caulk to seal the perimeter of the vapor barrier, but the stuff usually skinned over before I got the poly in place and didn't stick very well so I ended up using a lot more caulk than I wanted to in order to get the vapor barrier well sealed to the wall perimeter. The acoustic sealant sticks to the poly (and everything else) like crazy, so it's perfectly suited to the task and allows plenty of work time since it never skins over. Once the poly is up with a couple staples to hold it in place, the sheet is smoothed and tightened over the wall and stapled in place around the perimeter and every 12-inches or so throughout the field.

The final step is to "sweat the small stuff" which means going over the entire wall and seal any remaining penetrations and seams in the vapor barrier with tape. I use VentureTape® link opens a new window HouseWrap Sheathing Tape, which is not cheap, but it very sticky and pretty heavy (compared to plain old packing tape) so it works well. This is the very nit-picky step, since I tape every staple used to hold the poly in place, as well as the seams and big stuff. Once it's done, the result is an air tight, moisture proof surface, ready for the final wall covering (GWB, panelling, etc.).

click to magnify Wall insulation and vapor barrier (2 photos).

Insulating the Exterior Walls
As discussed above, the wall insulation is must be installed before completing the interior vapor barrier. For most of the wall insulation I chose John Mansville Formaldehyde-free™ Unfaced FiberGlass link opens a new window R-13 batts (rather than the pink stuff) to reduce bringing more Formaldehyde into the house. I also like it because it's white, and there's often long delays between getting the insulation up and sealed before I get around to applying the final wall covering. It sounds silly, but I can stand looking at white insulation for a while instead of a bunch of pink walls. The JM insulation also comes with a couple Easy-Fit™ batts in each bundle, which are perforated length-wise for when I need to insulate a non-standard width wall cavity.

Unfortunatly, I can only get an R-13 (3-1/2 inches) value for the walls, since I'm not re-framing the entire house with 2 x 6 studs to create the 5-1/2 inch deep cavity required for the recommended R-19 wall insulation value. I suppose if I'd added an inch of rigid foam to the exterior sheathing before I put up the siding I could have hit R-19, but I'm confident that my over-the-top vapor barrier will allow my insulation to perform at its best, so R-13 should do the job. Time will tell.

Insulating the Floor
Because the house has a crawl space, rather than a full basement, some consideration must be given to whether to treat the crawl space as conditioned space then insulate and seal the foundation and ground, or treat it as unconditioned space, leaving it ventilated and insulating and sealing the bottom of the floor joists. With radiant floor heat as our heat source, we had little choice but to insulate at the bottom of the floor joists. We also enjoy a very high water table here, so the ground in the crawl space is usually quite damp. Trying to make the crawl space an air-sealed conditioned space would have required installation of an underground drain system with multiple sumps, and since the house is the lowest point of the property, there's really no where to pump the sumps out to. The final solution is actually a combination of both schools of thought (seal and conditioned versus vented and unconditioned crawl space), which I arrived at to balance the need to insulate the radiant heating system as well as deal with the moisture in the crawl space. For details regarding the insulation under the floor, please see the HVAC Floor Insulation section, since the insulation system is an integral part of the heating system. I intend to add rigid board insulation to the crawl space walls, and already have heavy plastic sheeting on the ground under the hosue to help with moisture control. The crawl space is vented as well (for moisture), although the vents are closed in the winter.

click to magnify Under-floor insulation.

The interior of the floor still requires air sealing regardless of what's going on with the floor joists and in the crawl space. I don't roll plastic sheeting over all the floors, however the floor still gets a complete perimeter seal with caulk. Before the walls are covered, any space between the wall vapor barrier and the floor is filled with that nasty acoustic sealant, then the sub-floor sheathing is applied - either tongue & groove OSB sub-floor panels (for under the laminate flooring) or cementitious tile backer-board (for under the tile). The OSB or backer-board then forms a seal across the plane of the floor either with sub-floor adhesive under the OSB, or the thinset mortar under the backer-board. The finish floor is also sealed around the perimeter of the room when it's installed. The laminate flooring has a 3mm pre-glued foam backing and is caulked around the entire perimeter with 1/4-inch bead of acrylic latex caulk before baseboard trim in installed. Tile and grout is held away from the wall with a spacer (a 1/4-inch thick strip of plywood) during installation, then the remaining gap is also filled with acrylic latex caulk once the mortar and grout has cured. I use DAP® Alex Plus®link opens a new window siliconized acrylic latex caulk for all the perimeter floor gaps (and everything else that doesn't get the acoustic sealant, for that matter).

Insulating the Attic
Heat rises, so lets put lots of insulation in the attic, right? Wrong, mostly... Folks tend to put lots of insulation in the attic because it's easy to get at, not necessarily because of what's going on up there and how it affects the conditioned space below. If the interior is properly air-sealed (which ours is), then there's no chance for convective heat loss or gain through the attic. The problem is there's still an increased chance for conductive heat loss through the ceiling and framing into the attic, since the ceiling surface and framing are naturally warmer than other surfaces inside the house (convective heat transfer is how we all heat the house, remember, so that warm air rises in the home). Even more severe is the chance to reduce interior cooling efficiency in the summer when a super-heated attic conducts heat into the cooler home. So attic insulation is still a big deal, which is why the EPA recommends 12-15 inches of insulation (R-38) for attics.

Our ceilings are built with 2 x 6 joists, so the easiest place to start in the attic is with some 5-1/2 inch thick fiberglass insulation in all the joist bays. I used Owens-Corning® Pink Fiberglas®link opens a new window R-19 insulation for the first layer of attic insulation. The interior ceiling gets the same vapor barrier / air sealing treatment as the walls, with a little extra fussy attention paid to the recessed lighting fixtures. Recessed lighting is a notorious source of air leaks, so I selected ICAT (insulation contact, air-tight) fixtures, then caulked, taped and foamed even the tiniest openings in the fixtures during installation. The fiberglass insulation is then "fluffed" and carefully placed into every nook and cranny between the ceiling joists and other framing and fixtures in the attic. Another area the requires extra care is the area between the wall top plate and the roof. This critical junction contains a rigid foam vent to allow air flow between the soffit vents and the attic, so the insulation is cut at an angle and placed between the top plate and the vent shield, as well as in any voids between the shield and the framing members. Once all little bits are placed around the top plate, the rest of the insulation is easily rolled out between the joists. The result is a level R-19 insulated plane, even with all the ceiling joist tops - but we're not done yet.

The next step is to add another 12-inches of blown-in fiberglass insulation, using the Owens-Corning® AttiCat®link opens a new window insulation system. Rather than roll out additional fiberglass batts over the top of the joists, the blown-in material will do a superior job of filling any existing voids in the framing members, as well as fill any space around the ventilation ductwork. An additional advantage of the AttiCat® system is that the fiberglass will expand as it's installed, rather then slowly settle like blown-in cellulose insulation. I haven't done the blown-in installation yet (since the bedroom and living room ceilings haven't been removed yet), but the result should be a total R-49 value for the ceiling once it's finished.

click to magnify The installed Munchkin™ T80M.

Improving the Heating & Cooling Systems
Upgrading the heating and cooling systems would usally be an expensive proposition that most homeowners don't undertake lightly, but since we had a 50 year old furnace and no air conditioning when we started the renovation, this one's easy - we get to purchase the latest and greatest stuff, and enjoy sizeable rebates and tax credits in the process. For details of the upgraded heating and cooling equipment we're using, please see the HVAC section. Details of the high-efficiency indirect water heating system can be found in the Plumbing section.

High Efficiency Windows & Doors
All windows and doors were replaced with Marvin Integrity® link opens a new window Wood-Ultrex Energy-Star units. These are fiberglass-clad wood-cased windows and doors, with Low-E II Argon filled double pane insulating glass. Typical thermal specs for the units are U-factor: 0.30; R-value: 3.33; Solar Heat Gain Coefficient: 0.31 and Visible Light Transmittance 0.54 (depending upon the unit style and size, the values vary buy a couple hundredths of a point here and there). Each unit was installed and flashed according to the manufacturer's specifications (for complete installation details, please see the Windows & Doors section.

click to magnify One of the new windows.

Dealing with Moisture
With a totally air-sealed, conditioned space inside the home and piles of lofty fiberglass insulation in the walls and ceiling to prevent conductive heat transfer, we're faced with an additional problem of moisture in the walls and attic, which can lead to mold... that's bad. Some moisture in the wall and ceiling insulation is inevitable, since there's always some interchange of warm and cool air within the insulation layer. Condensation appears whenever warm, moist air meets cooler air that cannot hold as much moisture. In order to prevent that condensation from causing problems, the insulation materials should not absorb moisture (fiberglass cannot absorb moisture), and the moisture vapor needs to be removed from the insulation layer. If we encase both sides of the insulation layer in plastic sheeting, any moisture that's within the cavity will be trapped - this is where house wrap comes to the rescue. House wrap is a thin sheet of flashspun high-density polyethylene fibers that keep air and bulk water out of the wall, but allow moisture vapor to escape through microscopic pores in the material. The key to successful application of house wrap is understanding the difference between "bulk water" and "moisture vapor".

click to magnify House wrap on the West side.

House wrap is used to create the exterior layer of the thermal barrier, but it is not the "weather shell" for the building - that consists of the roof and siding materials. In order for house wrap to be effective, it needs to be applied to the building just as carefully as when creating the interior vapor barrier. All seams and penetrations in the material must be sealed with tape and/or caulk in order to prevent air infiltration into the insulation layer. When installing the final finish siding to the building, an additional step is taken to assist with moisture control which is to create a minute air gap between the siding and the house wrap to allow some air flow across the house wrap. This is accomplished by simply adding strips of building felt along the vertical surfaces of all wall framing members before attaching the siding. The top plate and bottom plate of the wall do not get the felt strips, since there has to be a way to get air behind the siding. When the siding is installed, all penetrations and vertical seams are caulked, however the top and bottom edges are left unsealed. The siding and roof overhang prevent bulk water from reaching the house wrap, but because of the small air gap, and moisture in the wall still has a method of escape.

The attic presents a different set of circumstances with regard to ventilation and moisture due to the amount of space between the weather shell (the roof) and the insulation layer (the ceiling) as well as the extreme temperature differentials that occur in the attic. The most practical solution to create a "cold attic" by ventilating the attic with outside air all year. When the attic is super-heated in the by the Summer sun, the warm moist air within will diffuse moisture vapor into cooler insulation layer at an alarming rate. Fresh air is brought into the attic through soffit and gable vents, and attic air is allowed to escape through a continuous ridge vent which alleviates the super-heating issue. In the Winter, any warm, moisture laden air that makes it into the insulation layer (although that shouldn't really occur with a proper vapor will be removed from the attic through the same fresh air ventilation system.

Indoor Air Quality
Once the thermal barrier is in place and the house good and tight, we're faced with a new set of problems with regard to indoor air quality and combustion safety. We use a Heat Recovery Ventilator (HRV) to supply fresh air inside the house without compromising our overall energy efficiency. The HRV also ensures combustion air for the gas stove is readily available, as well as to remove combustion pollutants produced by the stove. Combustion air and gases are self contained for the boiler, which employs a direct-vent sealed combustion system. Indoor Air Quality and HRV installation is fully addressed in the HVAC Ventilation section.

Efficient Lighting & Appliances
Wherever possible, we install Energy Star lighting fixtures and make use of Compact Fluorescent (CFL) bulbs. Of course, the most used lights in the home are the kitchen overhead lights and bathroom vanity lights, and those are unfortunately using standard incandescent (halogen) bulbs. The fixtures are Energy Star rated, but for recessed task lighting and seeing your face at 6 am, the current crop of CFLs just don't cut it. We've tried CFLs for the vanity, but they're not bright enough (the fixtures use candelabra-base bulbs, and there's still very few options available for a bulb that will actually fit in there). As for the task lighting in the kitchen, that's currently running PAR20, 50w halogen bulbs, although those are non-dimmable fixtures so we'll likely replace those with CFLs now that some newer, proper color temperature PAR20s are becoming available. Other recessed lighting also uses halogen bulbs, but we generally dim those fixtures by 50% or more, so I can live with that. The dimmable recessed lights in the bathroom do make use of R30 CFLs, and while the dimming performance isn't as nice as incandescent, they function well enough (and provide a better color temperature than incandescent). All other lighting in the house makes use of either cold cathode fluorescent bulbs, compact fluorescent bulbs, or standard bi-pin fluorescent bulbs.

Household appliances are another area where we've needed to purchase all new units during the renovation, so we've been able to select proper Energy Star rated appliances for everything. Major kitchen appliances include a microwave/range vent combination unit, a refrigerator, a gas range, and a double-drawer dishwasher. We also recently purchased a new Energy Star front-load washing machine (which automatically adjusts the water level based on the load), and a moisture sensing electric clothes dryer.

More photos and updates to follow as work progresses...