Attic Insulation Options Offer Different Pros and Cons

Attic insulation plays a critical role in home energy performance. In fact, most building scientists agree that the attic should be the first “target” area for insulation and air-sealing upgrades. Most homes are built with code-required minimum levels of attic insulation that are far below current recommendations established by the U.S. Dept. of Energy.

Homeowners considering an attic insulation upgrade have a number of different insulation materials to consider. Each attic insulating option has distinct advantages and limitations. Understanding these pros and cons can help you select the best insulation upgrade for your attic.

Fiberglass batts

Fiberglass batt insulation is popular because it’s affordable and universally available. Regardless of age, many houses have attics insulated with fiberglass batts. The batts are typically installed between attic floor joists, and unfaced batts are more common than faced batts in attic installations.

PROS: More affordable than other types of attic insulation. Best type of insulation for DIYers to install. Unlike blown insulation, batts can be lifted up and moved to provide access to the ceiling below, can lights and ceiling-mounted vent fans. Existing batt insulation can often be left in place when blown insulation is added to increase overall R-value in the attic.

CONS: Difficult to install correctly around obstructions. Voids where insulation is missing contribute to significant energy loss. Multiple layers of batt insulation are required to achieve recommended R-values in most parts of the country; this makes it impossible to use the attic for storage unless special platforms are built prior to insulation installation. Fiberglass insulation can’t stop air movement.

Blown insulation

Two main types of blown (or blow-in) insulation are commonly used: cellulose and loose-fill fiberglass. Both types are designed to be installed using special blowing equipment.

PROS: Installation can be completed quickly and affordably. Blown insulation typically results in more complete coverage than is possible with fiberglass batts.

CONS: A thick layer of insulation (at least 16 in. for northern parts of the U.S.) is required, and this makes it impossible to use the attic space for storage unless special platforms are built prior to installing the insulation. Cellulose and loose-fill fiberglass insulation can’t stop air movement.

Spray foam

Professional spray foam insulation contractors typically insulate an attic by applying a thick layer of spray foam between the rafters. Two types of foam are used: open-cell and closed-cell. Opinions vary as to which type is best in an attic installation, but closed-cell spray foam is used more frequently.

PROS: Closed-cell spray foam provides the highest R-value per in. (about R-6) of any attic insulation. It also creates an air and moisture barrier, so it eliminates the need for separate air-sealing work. Insulating beneath the roof deck instead of on the attic floor frees up attic space for storage and other purposes. This strategy also improves the efficiency of HVAC components (like air handlers and ductwork) located in the attic.

CONS: Most expensive attic insulation. A thick layer of foam applied to the underside of the roof sheathing can trap moisture and cause sheathing to rot.

Rigid foam

Rigid foam hasn’t been used as extensively for attic insulation until a most recent development. In one unique system, a proprietary rigid foam panel is fastened to the underside of attic rafters, forming an air and thermal barrier.

PROS: Provides all the benefits of spray foam, with the additional benefit of maintaining attic ventilation. The potential for roof sheathing moisture damage is eliminated. The rigid foam is faced with a radiant barrier that reflects heat for additional energy savings -another advantage over spray foam.

CONS: The system is available in limited areas, so it’s not as widely available as spray foam. Installation cost is greater than fiberglass batts and blown insulation, but competitive with spray foam.

Proper Roofing Ventilation: A Roofing Contractor Explains Its Importance

When it comes to home improvements, many homeowners feel that “more is better,” particularly when they are considering roof ventilation. In fact, that’s not always the case; you can have too much venting, the wrong kind or even two different kinds that don’t work well together. If your home is improperly vented, it can lead to excessive heat in your attic, which will force your cooling system to work overtime in the warm months. Excess humidity can also be a problem that leads to more serious complications such as rotting of the roof deck and mold growth, which can be dangerous to your house and damaging to your home’s walls.

To make sure your home’s roof is properly ventilated, talk to a seasoned roofing contractor who can explain the different types and determine which kind and how much you need for your house. A local roofing company can also discuss the costs and benefits of a new or upgraded venting system in your home.

Passive Ventilation

Most homes with asphalt shingles use passive attic ventilation to keep the area cool. Natural convection — the upward movement of air when it is heated — is the primary way passive venting cools things down. For larger areas or homes that are difficult to cool, a roofing contractor might add fans that use wind to increase pressure differences in the air and improve cooling. The air current that cools the attic can be improved by installing intake vents at the bottom to allow cooler air in, while the hotter air will rise and be released through ridge vents.

Powered Ventilation

Sometimes your roofing company will suggest a powered vent system. This is generally a good idea when your roof’s passive system isn’t sufficient or if your attic area is particularly hot during the day. Small motors mounted near the outtake vents pull hot air up and out of the space. It’s very important to understand the mechanics of this system in order to ensure that your home has sufficient intake vents under the eaves; otherwise, the forced flow of air could pass the intake vents entirely, defeating their purpose.

Combining Passive And Powered Ventilation Is A Mistake

If you’re concerned about your attic being too hot, consult a roofing company in your area. You may talk to a contractor who suggests that you add one or more electrical fans to the roof in order to improve the airflow. If you already have a passive system in place, however, adding a powered system is not the answer unless you are going to remove your current roof and start from scratch. It’s never a good idea to combine two very different types of ventilation, as they will most likely end up working against each other rather than solving any problems. In many situations, using two different types can void the warranty on your shingles, so be sure to discuss this possibility with any roofing contractor who has agreed to install new or additional vents on your home’s roof.

To ensure that you have the best ventilation system for your house installed, be sure to ask questions before signing a contract. It’s also a good idea to get at least one other quote just in case.

7 Things You Should Never Do When Improving the Efficiency Of Your Home

1. Tighten a home that has moisture issues

Energy efficiency can be directly related to the warm air leaking out of your home. So most of us understand that air sealing and tightening our homes will make them more energy efficient. That is correct, but it is extremely important to eliminate moisture problems before we do so. Moisture trapped within the home creates condensation, structural damage, mold growth, and poor indoor air quality. Sources of moisture can be dirt basements and crawlspaces, un-sealed concrete slabs or walls, fish tanks, cooking with gas, cooking without lids on pots, shower areas, excessive amounts of plants, greenhouse open to the living space, standing water, bathroom or laundry vents not vented to the exterior, uncovered sump pumps and many other sources. The best course of action is to eliminate the moisture source before air sealing the home. If you can’t eliminate the source, encapsulate it. If you can’t encapsulate it, try to diffuse it.

2. Replace the windows first

Windows are very costly. Rarely do windows pay for themselves in energy retrofits before the lifespan of the window is considered over. Who wants to wait 25, 35, or 45 plus years for their windows to pay for themselves? The current energy standards only require you to put R- 3.3 windows in your home. That’s hardly better then the R-2 double hung window that you currently have. The most cost effective solution for window retrofits is air sealing the window during installation, not the actual window itself. So before you replace those leaky windows, see if you can remove the trim and air seal around the window. If you have a broken window, or a window with condensation between the panes of glass that would be an appropriate time to replace the window. Also, if you have a very old home with weight and chain windows, it might be in your best interest to replace the windows. The weight and chain cavity of a window allows significant air leakage into the home and cannot be effectively sealed without changing the operation of the window.

3. Not have a qualified energy professional evaluate your home

Many contractors will tell you that you don’t need to hire an energy professional to evaluate your home. However, energy professionals are trained in both evaluation and safety. A good energy auditor will not only evaluate your home but provide diagnostic testing to locate the worst performing sections to tackle those first. In addition, an energy auditor should be checking your home for air quality issues like back-drafting furnaces, poorly performing ventilation systems, leaky gas lines, and excess toxins and moisture. They should be able to provide you with a prioritized list of energy improvements, and come back to test the air quality and heating system safety after the work has been completed. Simply adding more insulation to your attic without addressing potential problems is a waste of your time and money.

4. Insulate your attic without air sealing first

As I mentioned above, adding extra insulation does not mean that you are adding energy improvements. Attic spaces tend to have several openings between the living space and the cold attic. That air movement from the living space into the attic increases heat loss in your home and also transfers warm moist air to the attic. That warm moist air will often condense on the roof sheathing and cause premature roof failure and mold growth. Insulation is not meant to retard airflow; it’s meant to reduce conductive heat flow through the ceiling material. So if your insulation isn’t in full contact with your sheetrock or plaster ceiling it is not an effective thermal barrier. This can happen due to strapping on a ceiling or insulation that fits poorly within a space. Air is constantly flowing between the surface of the ceiling and the surface of the insulation taking heat with it. The areas around penetrations in the ceiling are drawing air, because heat rises, up through those holes with little resistance. Fiberglass insulation becomes a filter for that air, but does not stop it. Cellulose insulation can reduce the flow, but also does not stop it. So the first course of action when adding insulation to your attic is to air seal around all penetrations [pluming, electrical, mechanical, chimney’s, open wall cavities, etc] prior to adding a layer of insulation. Then be sure that the type of insulation you install will fit fully against the ceiling surface below.

5. Forget the attic hatch

As little as a 7% void in insulation can cause up to 50% of the heat loss through your attic. Having an un-insulated attic hatch adjacent to your R-49 attic space can result in a significant amount of heat loss. Your heating system will work hard to continue to heat that hole in your ceiling. The attic hatch will be constantly giving heat to the attic and requiring heat to stay warm. Sometimes there is a fiberglass batt positioned on the top of the attic hatch, but the first time someone goes up through the hatch the batt is moved to the side and rarely replaced. Even if your attic hatch has insulation on it, the hatch is rarely air sealed allowing a significant amount of heat to enter the attic space around the board or sheetrock that acts as your attic hatch. So, even if you do have a fiberglass batt on top of your attic hatch, if it is not air sealed, that insulation is doing nothing.

6. Pretend the basement does not exist

Basements are an integral part of a building envelope, and although we like to pretend they do not exist they are some of the leading contributors to energy loss in a home. Concrete has virtually no R-value, so any section of above grade foundation that you have is continually leaking heat to the exterior of your home. You may notice that your flowers bloom early in the spring, and the snow melts directly against your foundation sooner then other areas. Basements also tend to be the place where we store our chemicals, firewood, paints, and install our heating systems. If you have poorly installed ductwork in your basement you can be transferring all of those indoor air pollutants directly to your living spaces. Any holes between the basement for plumbing, electrical, and mechanical directly introduce the moisture and toxins from your basement into the rest of your home. And insulating the basement ceiling isn’t going to stop that airflow, and often times can lead to frozen pipes and performance issues with your heating system. So before you say you want to do an energy project, but you don’t want to address your basement, remember that you could be creating a new issue that you did not have before.

7. Ignore the air barrier between the garage and living space

And last, but certainly not least, is ignoring the reasons why new construction codes require you to have a separation between your living space and your garage. For code purposes, several of the requirements relate to fire hazards. However, we have also learned in recent years, with the influx of tighter homes, that contaminants in the garage often leads to poor indoor air quality. Your car continues to give off carbon monoxide for hours after it is turned off. Similar to your basement, your garage is where you tend to store chemicals and gas for your lawn mower. For these reasons, it is very important that you have a continuous air barrier between your garage and living space. This includes attached garages and tuck under garages where the garage is below with a living space is above.

Remember, your house is a system. Every part is directly or indirectly related to some other part. So hiring an energy professional to help you create a safe, comfortable, and energy efficient home isn’t just important, it’s critical.