Insulation & Ventilation


  • Real energy savers
  • Real energy savers revisited
  • Understanding Insulation
  • Attic Ventilation
  • House Wrap

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Real Energy Savers

Why the title Real Energy Savers? Because the tips listed below go beyond the standard tips which are usually recommended. Standard tips include: insulating the attic, wrapping the water heater, and adding storm windows. Implement these real energy savers and start saving big $$$.

1. Outside air for heater burners with an appropriately sized trap (Gas, oil, wood, or coal) 

Combustion needs fuel and air. If you use air for combustion from the basement and house, you create a negative air pressure system inside the house which will draw or induce outside air to be pulled into the house. 

When cold outside air mixes with warm inside air it lowers the ambient house temperature and causes your heater to go on or stay on.

Outside air ducted to the air intake of the burner will reduce the fuel consumption approximately 17% in an average house.

An appropriately sized trap is necessary to resist the colder outside air from falling in the basement continually in the heating season. Look to a mechanical tradesperson for your specific size.

2. Dampers for furnace and water heater flues

Open flues and chimneys create an opening in the house which allows the thermally buoyant warm air

from a basement and/or house to rise out of the chimney. Losses are significant due to the thermal momentum created by warm chimney walls.

Warm air loss draws cold outside air into the house and is a chronic waste of energy.

Proper dampers on the flue will reduce these losses considerably.

3. Reduce thermal air loss vertically through the house and in the walls of the house

Warm air will rise in any opening in a house (i.e., plumbing or electrical chases, balloon-framed houses, masonry walls that are stripped on the inside to receive plaster or drywall and any openings around windows, doors, baseboards, trims, etc.).

Warm air loss is the largest and single most wasteful energy loser in some houses. It also creates an inducement which draws cold outside air into the house.

The solution to this problem is to close any openings that you find. The most effective way to do this is with a blower door, infrascanner and monitor. The blower door is a large panel with a fan that adjusts to a doorway. The infrared scanner with monitor allows you to see where the heat loss is. Once you know where you are losing warm air, it s relatively easy to reduce thermal air loss.

Commercial companies can do the scans, reduce the air loss, and re-do the scanning (Look in the yellow pages under Energy Conservation and Management Products and Services).

4. Insulation

Ceilings above the living space should have 6 to 12 of insulation.

Vapor barriers should be installed on the warm side of any insulation situation. The only function of insulation is to reduce thermal conductivity. It does not stop air infiltration. 

Though wall insulation is beneficial, it is only recommended when you can blow in 3 1/2 and when the workmanship can be verified by an infrared scanner to check for leaks and uneven application.

5. Storm windows

Storm windows have two basic functions: (1) reduce air infiltration and (2) protect the main windows from the weather.

Storm windows should be installed on wood thermal breaks if the main windows are metal.

Storm windows have very little effectiveness as far as saving energy if you do not address energy

saving tips #1, 2, and 3 listed above. The negative air pressure system that tips #1, 2, and 3 create will simply cause cold air to be drawn into the house from some other place. 

6. Weather stripping

Give doors and windows a tight seal with weather stripping. This will reduce air infiltration. To realize the maximum benefit from weather stripping you must implement tips #1, 2, and 3.

Look for more real energy savers in a future column. 

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Real Energy Savers Revisited

The energy saving tips listed below go beyond the standard tips which are usually recommended.

Standard tips may include: insulating the attic, wrapping the water heater, and adding storm windows. Implement real energy savers and start saving big $$$. 

1. Siding

The main function of siding is to keep the weather out of the house. The inability of siding to keep cold air from getting behind it makes it practically useless as an energy saver.

Note: Insulated aluminum siding does not insulate at all because air easily gets behind the siding.

To reduce air infiltration into the exterior walls you must wrap the house before you install any siding. The wrap must be able to stop air and cannot be allowed to trap moisture permeating from the inside of the house. DuPont s Tyvek is an excellent material for this use.

2. Set-back thermostat

It s advantageous to have the heat at lower settings when not at home or sleeping. With this type of thermostat, you can select in advance the times you would like the heat to go on and off.

3. Computer thermostat

This type of thermostat will allow you to program much more information than a set-back thermostat,

such as different settings for weekdays and weekends.

The computer thermostat is especially advantageous with a heat-pump because you can program it to

override back-up electric heat unless the outside thermostat requires it.

NOTE: One of the most inefficient aspects of a heat-pump is the improper use of the thermostat. The computer type thermostat can enhance its efficiency.

4. Ventilation

Condensation is caused when warm air (which has more ability to hold water than cold air) moves into

an area with colder air.

Large quantities of air are needed to carry off air that may become saturated. The best way to develop good ventilation is with high-low ventilation (i.e., ridge vents and soffit vents).

Note: Insulation that absorbs moisture from saturated air has little or no effectiveness as an insulator and can actually increase the conductivity of the insulation. 

The formula for proper ventilation is one (1) square foot of clear air distributed 50% high + 50% low

for every 300 square feet of attic space. Additional ventilation is necessary if the insulation does not have a vapor barrier.

5. Heaters

Heaters waste 25% to 50% of your total heating fuel.

The design of the heater, type of burner, and fuel used will dictate how much waste goes up the chimney.

The main questions to ask when you are in the market to buy a heater are:

  1. What is the temperature of the flue gases? This will be dictated by the heat exchanger or boiler design. The lower the exhaust temperature, the more efficient the unit will be.
  2. What is the overall efficiency, including fuel, chimney, and heat transmission losses? 

6. Water heaters

The most economical way to save energy with water heaters is to keep the temperature at approximately 120 to 130 degrees, depending on your usage demands.

Wrapping water heaters is OK. However, the savings are minimal in 95% of the cases.

When buying a new water heater, you should buy a heater only as large as you need (i.e., an average family of four will get along satisfactorily with a 30 gallon gas-fired water heater).

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Understanding Insulation

One of the ways a house loses and gains heat is through conduction. Conduction is the movement of heat through solid objects, such as walls, the ground, floors and ceilings. Heat always moves toward the cold, trying to equalize the temperature, and does move through solid material. Heat inside a warm house will always try to escape and, in the summer, the heat outside tries to get in.

Insulation in floors, ceilings and walls is helpful because it traps tiny pockets of air that retard the transfer of heat. Insulation won’t stop heat entirely, but will slow it down.

Insulation’s effectiveness is indicated by its "R-value", which is its ability to resist heat flow from warmer to cooler areas. The higher the R-value, the more effective the insulation. It is important to remember that a material’s insulating ability is based on R-value, not thickness.

Types of Insulation

  • Batts and blankets-Fiberglass. The R-value per inch is 3.1 to 3.5. It is best suited for standard joists, studs or rafter spacing in attics, walls and the underside of floors.
  • Loose fill - Cellulose, fiberglass and vermiculite. The R-value per inch is 2.2 to 3.7. It is best suited for non-standard spacing, infill of block walls and spacing between joists that have obstructions.
  • Rigid board-Polystyrene, polyisocyanurate, urethane and bead board. The R-value per inch is 3.5 to 5.5. It is best suited for basement walls, foundations, exterior walls, interior walls and cathedral ceilings. 

Where to Add Insulation to a Home

  1. Living area ceilings below an unheated attic.
  2. Living area floors above unheated basements, crawl spaces, garages and open porches.
  3. Uninsulated exterior frame walls.
  4. Between sloping rafters. Be sure to leave an air space for ventilation between the insulation and the roof sheathing. (Select insulation accordingly.)
  5. In the back of band or header joists around the perimeter of the basement.
  6. Basement walls when below-grade space is finished for living purposes or when the basement doesn’t enclose a fossil-fueled furnace or boiler (gas/oil).
  7. Basement walls where the above-grade exposure exceeds 50 percent of the interior wall surface.

When adding insulation in the attic, keep at least 1 1/4" space between the insulation and the sheathing to allow air for the soffit/eave vents to flow to the ridge and/or gable vents.

The Cost to Add Insulation

You can expect to pay 65 cents to $1 per square foot for insulation, including labor and materials. 

In the attic, a contractor will install about 9" of insulation. If you have a 1,000-square-foot attic at an insulation cost of $650 to $1000, you can expect savings of $125-$200 per year, depending on the climate. Your payback would occur in five to six years.

Insulating walls is generally an economic loser. Also, the walls are much more difficult to insulate. It requires drilling holes, filling walls and using an infrared scanner. Walls also have much more square footage to insulate than the attic. With 4,000 square feet of walls in an average house, the cost may be $3,500-$4,500. You won’t break even on your investment for 15-20 years. A better option is to address the air infiltration and air loss.

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Attic Ventilation

One of the most frequent, and least recognized, problems home owners have is inadequate attic ventilation. 

Poor Attic ventilation problems can lead to excessive heat in attic spaces in summer, which will prematurely fatigue a roof require additional cooling of the living spaces below. During the winter, moisture from indoor activities migrates from the living spaces to the attic - delaminating plywood, rotting roof sheathing and framing members.

How To Tell:

Rusted nails and stained roof sheathing are initial signs of a ventilation problems.

Two tests help determine if there is sufficient ventilation in an attic.In the winter, look for moisture or frost on exposed nails at the underside of the roof sheathing during very cold weather.

On a warm, windless summer day, there should be a maximum 10 to 15 degree temperature difference between the air in the attic space and the outside shade.

Here are some cures for poor attic ventilation:

  • Ventilation Systems: Ridge and soffit vents allow natural ventilation of the attic. Cool air enters at the soffits under the exterior roof overhangs. As this air warms, natural convection pushes it to the ridges at the top of the roof where it vents to the outside.
  • Power Fan: During summer operation a thermostat automatically operates a roof or gable-mounted fan as needed to force air circulation. For proper moisture control in winter the fan should be operated by a humidistat, placed at the lowest point in the attic on the north side, or a clock timer for two (2) minutes each hour during cold weather.
  • Blocked Vents: Clearing up blocked soffit vents often cure a ventilation problem.

Adequate attic ventilation all year around is important to the long term health of your house, reduced heat and cooling loads, and for optimum interior comfort.

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House Wrap

Putting a housewrap on a home is much like putting on a windbreaker on a windy day. So, why does a new home need a housewrap? Homes have thousands of places where building components come together, and everywhere that they join, there's a crack or a gap. That causes air to filtrate in, which causes you to be more uncomfortable and raises your energy bills. It's important to control air infiltration, because every time that air infiltrates into a house, that pushes out the air that has already been paid for to heat and cool.

Perhaps you have heard a house whistle, heard air blowing through it, or have felt wind coming through an electrical outlet. A housewrap will prevent all of these symptoms. It seals up a lot of those cracks and gaps that would be difficult to do with caulking. Eventually, caulking wears out; where an air barrier wrap, it's there for the life of the home.

When a house is wrapped, a builder takes the housewrap and wraps it around the entire home. They then return and X-cut around the windows and doors and flash around the windows. This process allows everything to be covered.

If a new home does not have a housewrap, it will lose energy. For example, if there is an R-13 wall and a 9-mile-an-hour wind blowing across the home, the apparent R-Value of that insulation is reduced down to about 5, More than 50% cut in R-Value. Lack of a housewrap is one reason why one gets cold even in a brand new house, or gets warm in the summertime.

Moisture has to be paid attention to since there is new moisture every day inside a house, with showers running, pots and pans boiling water, people just talking. An average family puts out about 70 pounds of moisture a day, and it's important that moisture has a way to get out of the home.

Depending on the part of the country, and a variety of other circumstances, a homeowner can save several hundred dollars a year on energy bills. And insulation of a housewrap probably will not cost more than $500.


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