Why is my Home so Hot? Do I Need Attic Insulation?

    

why is my home so hot?

 

You may find it interesting to learn that very few homes have adequate attic insulation. In fact, the North American Insulation Manufacturers Association estimates that 90 percent of homes in the United States lack the recommended amounts of insulation.

This is unfortunate. The right attic insulation, properly installed and with a high R-value, will make your home more comfortable even as it cuts your energy costs. At this very moment, you may be sending conditioned air right through the attic and into the atmosphere. Certainly, there must be better ways to use the money spent on this wasted energy!

In far too many homes throughout the area, furnaces and air conditioners are working overtime to compensate for inadequate attic insulation. Just like workers who enjoy the extra pay for overtime work, utility companies enjoy the extra profits generated by the "overtime" your stressed out HVAC system is putting in!

 

What Does Attic Insulation Do?

The reasons for increased attention on attic insulation are many. Updated building codes require greater energy-efficiency. Consumers grow weary of rising utility bills. Homeowners want to limit their CO2 emissions.

Insulation slows down the transfer of heat from one space to another. Effective insulation provides R-values that significantly minimize heat loss and heat gain depending upon outdoor weather conditions.  Properly installed attic insulation also minimizes air leaks to promote true energy efficiency.

attic insulation

Upgrading your attic insulation can put a substantial dent in those utility bills. In Maryland, for example, state building codes reflect 2012 International Energy Conservation Code (IECC), a significant upgrade from the requirements of 2009 IECC. In fact, compliance with 2012 IECC generates a 30-year lifecycle cost savings of $5,300 on average across the state, according to the Maryland Energy Association.

Another source estimates that increasing attic insulation from R-11 to R-49 in a smaller 800 square-foot attic can still save $600 per year. Even more modest increases in R-value can easily cut heating and cooling costs a couple hundred dollars per year. The Department of Energy estimates that energy savings of 10 percent are possible, year after year. This means that you'll typically recover the cost of adding attic insulation - it is just a matter of time before you do.

Types of Attic Insulation

At EnergyStar.gov, you'll find a table of recommended R-values for attic insulation. You will see that our area is in Zone 4. In older homes with the typical 3-4 inches of attic insulation, the chart suggests the addition of added insulation with an R-value of 38.

energy-star-add-attic-insulation

When you select insulation, look for other important features like:

  • A warranty from a reputable, well-known manufacturer
  • Moisture resistance
  • Resistance to mold, mildew and bacterial growth
  • Fire resistance

Finally, make a healthy choice. A recent report from Energy Efficiency for All asserts that fiberglass insulation is the healthiest insulation option.

There are five major types of insulation used in homes:

  • Blanket batts and rolls
  • Blown-in loose-fill insulation
  • Spray foam insulation
  • Reflective or radiant barriers
  • Rigid foam panels

For more detailed information about home insulation, consult Energy.gov.  

Insulation installers must cope with common challenges like recessed lighting, electrical boxes, odd-shaped spaces along the attic perimeter and attic stairways. Irregular spaces and attic penetrations may very well dictate the type of attic insulation you should consider.

Blanket batts and rolls

Blanket batts and rolls insualtion

Although batts and rolls are typically fiberglass, they may also be fabricated from cotton, mineral wool or cellulose. Since they are pre-cut to standard 15-inch or 23-inch widths, you must have an attic with standard joist spacing to make effective use of batts/rolls. Standard joist spacing is either 16-in on-center (o.c.) or 24-in o.c.

Batts and rolls may be appropriate when there is no existing attic insulation. There is less cutting required in attics with relatively few obstructions. Attics with adequate headroom allow installers the room they need to do their work.

However, to cope with obstructions, penetrations and irregular spaces this type of insulation must be accurately cut to size with a utility knife. Inaccurate cuts either leave gaps or cause compression that reduces R-values. Installers need protective gear to avoid lung irritation from fibers released during the process.

Also, thermal bridging is an important consideration when batts or rolls are merely fitted between studs or rafters. When this is done, cold air can transfer from one space to another through the wood.

Regular fiberglass blankets and batts typically offer R-values of 2.9 to 3.8 per inch. However, some high-performance blankets and batts offer R-values of as high as 4.3 per inch.   

Blown-in loose-fill insulation

Since loose-fill insulation is blown into place, it is ideal for insulating small and irregularly shaped spaces. It is easy to use in attics with numerous obstructions. It is also effective in supplementing existing insulation, particularly because it fills in gaps in the existing insulation. For example, if you currently have batts between attic joists, you can simultaneously increase R-values to recommended levels and fill in gaps by blowing in loose-fill insulation. Loose-fill insulation is also an excellent option if you have an attic with low clearances and minimal headroom.

The insulation itself is usually fiberglass, cellulose, cotton or mineral wool. R-values range from about 2.2 to 3.8 per inch. Fiberglass insulation is made from recycled glass or sand that is melted and spun into extremely fine fibers. Installers need to use protective gear to avoid inhalation of fiberglass fibers.

Cellulose insulation is made from recycled post-consumer paper. It requires treatment with chemicals to make it insect and fire-resistant.  Cotton insulation comes from recycled denim. Mineral wool is usually fabricated from slag obtained from blast furnaces.

One example of loose-fill fiberglass insulation is Pro Cat from Owens Corning. It is code-compliant, and it is SLS-certified to average 55-percent recycled content.

Spray foam insulation

spray-polyurethane-foam

Spray foam is limited in some attic applications because it cannot be sprayed over porous materials like existing batts. However, it is still an attractive option for insulating difficult-to-reach and irregularly shaped attic spaces.

Spray foam insulation consists of liquid polyurethane sprayed onto firm attic surfaces. As it comes out of the nozzle, it greatly expands and hardens. The liquid is delivered through a hose from a tank typically positioned on the driveway or another firm surface.

There are two types of foam insulation: open-cell and closed-cell. The latter type is denser, and it provides an R-value of around 6.2 per inch, making it one of the most effective insulators on an inch for inch basis. It is also more expensive. Open-cell foam insulation offers an R-value of about 3.7 per inch.

Radiant barriers

attic-radiant-barrier

This type of attic insulation is somewhat more common in hotter climates. The reflective barrier typically consists of a layer of aluminum foil over either polyethylene bubbles or kraft paper. The concept is different than that guiding other types of attic insulation. R-values do not apply since radiant barriers to not manage air flow. Rather, the intent is to reflect heat away living spaces. Such barriers are positioned between attic joists, rafters and/or beams.

Rigid foam panels

Rigid foam panel attic insualtion

The use of traditional methods of insulation is often impossible when a residence lacks an attic. For example, if your home has an unvented low-slope roof, you can still increase R-values through the addition of rigid foam panels, particularly with unfinished ceilings. With R-values of R-4 and R-6.5, these panels are effective insulators.

Such panels are made of either expanded polystyrene (EPS), extruded polystyrene (XPS) or polyisocyanurate (polyiso). They address concerns about thermal bridging since they typically cover ceiling elements made of wood, steel or any other material.

Problem insulation

For many years, vermiculite was used to insulate many attics. If you have vermiculite insulation in your attic, it needs to be tested for asbestos. Vermiculite itself is safe, but some of it came from a mine in Libby, Montana, where its proximity to asbestos became a key health issue. The issue does not arise with vermiculite from other mines, like those in Enoree, South Carolina and Louisa, Virginia. If you have vermiculite tainted with asbestos in your attic, it needs to be removed by specialists before you get new attic insulation.

Fully Insulating Your Attic

There's insulation, and then there's insulating. Both are important. The latter focuses on all the nooks and crannies that air can seep through. In a typical attic, there are usually many of them. It is always important to seal gaps with fire-resistant materials like the right expanding spray foam, fire-blocking caulk and furnace cement.

The following areas require careful sealing:

Pipes, exhaust fans, wiring and ducts

installing insulation on pipes in the attic

Narrow gaps around obstructions and penetrations are typically caulked, while wider gaps are usually filled with expanding spray foam. You'll usually find cracks around bathroom exhaust fans, plumbing vent pipes and ceiling can lights. It's important to box out light fixtures and electric boxes if this has not been done in the past. A safety gap several inches wide keeps insulation away from hot light fixtures.  

Partitions and walls

The design of certain interior walls and partitions allows conditioned air to leak into the attic, wasting energy in the process. Therefore, cracks between drywall and partition top plates need to be sealed. Holes for electric wiring drilled in top plates need to be sealed up as well.  

Attic windows

Gaps around window casings are usually sealed with spray foam, while gaps around the jambs and sash are often sealed with foam weatherstripping.

Chimneys and flues

Chimneys and flues that pass through attic spaces are a key source of leaks as well. The right combination of furnace cement, metal flashing and high-temp caulk will address these problem areas. Chimneys act as a thermal bridge that quickly transfers heat in and out of your attic space, countering the positive effects of a well-insulated attic. Therefore, unused chimneys should be removed.

Vapor barriers

Any attic insulation project requires attention to vapor barriers. For example, the foil or paper facing on certain types of batts/rolls is a vapor barrier. So too is the polyethylene sheeting often used under loose-fill insulation. In colder climates like ours, this vapor barrier should be placed on the warm side of the insulation. This keeps warm, moist air away from the insulation itself. It also helps to keep the conditioned air where you want it, in your living space.

By controlling airflow in a more precise manner, a well-insulated attic reduces drafts and increases the comfort of home occupants.

 

A Complete Insulating System

It is important to recognize that attic insulation is just one part of a complete system of managed airflow. For example, the open space above the insulation needs to be sufficiently ventilated to prevent condensation in the insulation. Soffit vents and baffles between rafters allow fresh air into the attic, while exhaust vents allow it to escape. Proper air flow keeps insulation dry and functioning with maximum effectiveness. Although it may seem obvious, exhaust fans must always point outside, not into the attic. 

When insulation gets wet, it quickly loses its capacity to insulate. Trapped moisture may also encourage mold growth in the insulation or elsewhere in the attic. Any effort to add insulation to the attic should begin with the repair of any roof leaks. Stains on attic joists, or on the underside of sheathing, point to roof leaks. Although attic insulation in often water-resistant, moisture is still a problem. First, it quickly reduces the R-value of the insulation, which increases utility bills. Second, moisture that does not routinely evaporate through proper attic ventilation may lead to mold or mildew.

Properly placed exhaust fans, baffles and intake vents are all essential components of a good attic ventilation system that allows insulation to perform as intended.

Contact BRAX Roofing Today

BRAX Roofing is a full-service roofing contractor serving Maryland, the District of Columbia and Virginia. At BRAX, we proudly install Owens Corning Pro Cat fiberglass insulation. Owens Corning is a leader in fiberglass insulation, and rightly so - the company invented it 75 years ago.

We'd welcome the opportunity to check out your attic insulation and offer our professional recommendations. To ask your questions, or to schedule a visit with our certified inspector, please contact us today!

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About The Author

Ben Matthews is a managing partner at BRAX Roofing, a multi-faceted company that focuses on residential and commercial roofing throughout Maryland and Washington DC. Having obtained the highest certifications in roofing from leading manufacturers around the country, Ben takes pride in providing BRAX Roofing customers with top-quality exterior home improvement service and expertise.