The Obama Administration has finally unveiled its Homestar retrofit rebate package. Also known as the “cash for caulkers” program, it offers rebates that cap at about $3,000 for most energy upgrades. With luck, that will be enough cash to prime the retrofit market.
That’s where you, the builder, come in. If you do your homework, you can make an economic argument for weatherizing your client’s entire home, regardless of whether the government is paying half the bill. In many cases, you can save them enough on heating, cooling, and electricity to pay for those additional products and labor in just a few years. How many years? That depends on the severity of the local climate, extent of the work, and condition of the existing home. Often, the less energy efficient a home is to begin with, the faster the owner will recoup retrofit dollars.
The System Thing
You’re probably sick of hearing about the house “as a system.” It’s a dull phrase, yes, but it’s the only way to approach energy retrofits. Old homes are tougher to green than new ones. Why? Because new homes tend to have a high level of consistency—the same insulation throughout, the same sealing methods and even framing patterns. Old homes promise none of this predictability. This can cause problems. You may blow an attic full of insulation, only to find that the house still feels drafty, because the furnace has no fresh air intake. Cold air is rushing in around the old windows. Or you may tighten the whole envelope using caulks, wraps, and foam, only to discover that conditioned air is rushing out the central fireplace, which lacks a decent damper.
Of course, performing a home energy audit—preferably with a blower door test—can alert you to some of these potential pitfalls. Once you know the home’s energy flaws, the challenge is to improve energy performance without creating moisture, air quality, or mold problems.
You may find that textbook solutions from the DOE and other sources don’t always look at the whole house as an integrated environment. Charts and tables show where air leaks occur, but not which systems are codependent. But few products (with the possible exception of energy-efficient electrical appliances) stand alone.
With that in mind, we looked at weatherization from a different angle: Instead of simply patching up bad building science in an old building, why not add the high-tech features it needs to go toe to toe with any modern green building?
Taking a radical step such as removing ridge vents and soffits may mean getting out of your comfort zone. It may call for re-educating local code inspectors, along with homeowners. But as a Green Builder reader, you’re not the average contractor. Go get ’em!
Unvent the Roof
Until the advent of spray foam insulation, this is not something we would have recommended. However, spray-in foam products such as have changed the rules. The expansion characteristics of these products, combined with their ability to reduce air infiltration in the tricky area where rafters meet top plates, mean it’s possible to completely change the dynamic of an attic space. Although this process costs more than adding attic blankets, it has several inherent benefits to the homeowner, including:
Wrap the Walls
- Energy savings. No longer will the ridge vent act as a conduit through which to create a “stack effect,” where indoor air leaks through light fixtures and wall cavities into the attic, to be carried outside.
- Ice dams solved. Roof surfaces will remain relatively uniform, solving the problem of roof runoff over a warm roof freezing as it hits cold eaves.
- New living or storage space. Because the attic is now a conditioned space, it can be used as storage, or, if head height permits, as a bonus space. In the latter case, however, be sure to provide for adequate egress in case of fire.
- HVAC efficiency improved. If the homeowner wants to run a heat pump, HRV or other appliance in the attic space, it will now operate without competing with outdoor air.
Building science has shown that reducing air infiltration is a key component of a whole-house retrofit. In older homes, walls are ripe for tightening. Simply by adding house wrap, taped at the seams, you can reduce air infiltration significantly. Alternately, adding rigid foam will increase overall R-value. Keep in mind that when applying closed cell foam to walls, ventilation and moisture control for the whole house will need to be planned carefully.
Re-wrapping or insulating an old home, of course, is no small job. It can also result in a lot of waste, especially if you plan to tear off old vinyl siding and replace it with new vinyl, or something more sustainable, such as pre-primed wood. Unfortunately, few places will recycle vinyl. A greener option would be to remove the siding and re-use it.
Apply Vapor Barrier Paint
In older homes, moisture in the form of vapor will often move through plaster or drywall and condense within the stud space. Drywall also acts as the primary barrier to air infiltration in old homes without house wrap. A study by G.K. Yuill at Penn State in 1996 found that drywall accounted for 77% of the wall’s resistance to airflow. You can raise that resistance by applying vapor barrier coatings. These coatings typically reduce the perm rating of the wall to about .6 (equivalent to adding 2 mil of polyethylene sheeting). Vapor barriers have the added benefit of making rooms feel warmer—perhaps because the coating traps moisture in living areas. One popular brand: Glidden 1060 Vapor Barrier. It has VOC content of 100g/liter.
Supply Fresh Air to HVAC—and Resize
Too often, older homes are not equipped with a fresh air intake for combustion devices such as forced air furnaces and boilers. In a leaky, drafty home with newspapers stuffed into wall cavities as insulation, this is no big deal. But once you begin to add insulation and remove air leaks, the furnace starts to behave like a blower door—literally sucking the air out of the room. At the least, this can pull unconditioned air in from outdoors. At worst, it can fill the house with poisonous backdraft gases from the flue. Either outcome is undesirable. Your best bet is probably to have your HVAC installer make a small, dedicated fresh air return. Another major energy improvement you can make is to evaluate the post-retrofit energy requirements of the home and replace the boiler or air conditioner with one that is properly sized. BaySystems offers an HVAC design service along these lines called Energywise, which works in conjunction with its spray foam insulation system. .
Reflect on Roofing
According to builders I’ve talked with, the main reason reflective roofing hasn’t caught on in the south is client taste. People don’t like white roofs, even if those roofs will save them up to 30% on their energy bills. But roofing manufacturers such as CertainTeed have come up with a way to slay that dragon—by creating roofing products that look relatively dark, but contain reflective granules that reflect heat.
One thing to keep in mind when looking at reflective roofing: According to the DOE, energy savings will be largest on roofs that are the most lightly insulated. So if you’re planning to spray foam a roof to superinsulate it, that reflective surface may not change the home’s energy bills. So why pay more for reflective roofing? Because you no longer have a vented roof, and excessive solar heat has been shown to shorten the lifespan of dark colored asphalt roofing. Also, it’s probably not good for the durability of spray insulation—however stable—to be exposed to year after year of high temperatures.
As much as 22% of a home’s energy can be lost in the top two feet of an uninsulated foundation wall. When you consider that 10” of concrete has an R-value of about zero, this makes sense. By covering the above-grade section of conditioned crawl spaces and foundations with rigid insulating material, you create a critical thermal break. Insulating below grade portions of the concrete also saves energy, of course, but those temperature differences tend to be mitigated by the surrounding soil, so the bang for the buck is less. You might also consider using some of the insulating techniques developed for shallow frost foundations, where foam extends horizontally out from the wall at a shallow depth, reducing the concrete’s exposure to temperature extremes. Various brands of rigid insulation are suited to the task, including products from Dow, Owens Corning, and Horizon.
Rethink Electric Hot Water Tanks
One of the most wasteful of home appliances, element-based electric hot water heaters, needs to be phased out. Depending on budget, you can insulate the existing tank, replace it altogether with a super-insulated version, or install an “on-demand” unit—or one of the new self-contained heat pump models.