September 2006 Edition 

Hot Garage

Our garage heats up to over 100 degrees in the evenings. Where is the heat coming from, and what can be done to eliminate it?           

My garage also gets unbearably hot in the evenings. The heat buildup is a combination of two things.


First, the garage is not conditioned (heated or cooled), and the afternoon sun is penetrating the walls and ceiling. This type of heat transferance is called radiation. The heat passes through the uninsulated walls and ceiling into the garage.           

Second, you park your hot automobile in your garage and most likely close your garage door. The automobile acts like a space heater and can greatly increase the temperature of the garage.   

According to the building codes, your garage must be totally separated from the rest of your home by a 20 minute firerating. You cannot just vent the heat into a common attic because a fire could spread from the garage to roof framing over the rest of the house. What is needed is a vent from the garage directly to the outside of the structure. You can accomplish this in three ways.


If the garage has a separate attic area, make sure the attic is well ventilated with soffit vents along the eaves and either gravity vents or a continuous ridge vent. The more attic ventilation, the less likely the heat will enter the garage. Adding ceiling insulation will also help.   

The next step is to add an exhaust fan through an exterior wall. This is more complicated because you must add an electrical circuit, cut an opening through an exterior wall and provide some type of opening for the air intake. Most exhaust fans are thermostatically operated and set the thermostat between 90 and 100 degrees.

Bonus Room Complaints

Our bonus room is the only room we have problems heating and cooling. What can we do to solve the problem?   

Bonus rooms are a popular feature for homebuyers. The additional space, usu­ally over a garage, is nice to have for an office, playroom or extra bedroom. Bonus rooms that are too hot in the summer and too cold in the winter are also one of the most common complaints by homeown­ers. About 55% of the customers who have had DigitalAira Homescans have called because of complaints about comfort and high bills. Many of these complaints are related to bonus rooms. 

Unlike other rooms in the house, a bonus room over the garage has unconditioned space all around it, including under the floor. Because of this, it starts out having more heating and cooling demands for its size. In addition, these rooms frequently are not properly insulated, particularly between the floor and the garage, and often have a number of air-infiltration paths, usually from plumbing and wiring penetrations that aren’t properly sealed. 

Builders often put the floor insulation on the garage side of the sheetrock when it should always be next to the part of the house that’s warm in the winter. Because the insulation is lying on top of the garage-ceiling sheetrock, a gap is formed below the bonus-room floor where air can move. Moving air doesn’t have any insulation value, and in summer that space forms a path for warm air to rise to the bottom of the floor. While the insulation should be attached to the floor, in an existing house you may want to have a contractor blow in additional insu­lation between the garage and the bonus room. This procedure can be costly, so it’s best to determine if the level of dis­comfort outweighs the cost before you make any decisions. 

Bonus rooms over the garage and in attics often have ceilings that follow the pitch of the roof and knee walls, the short walls below the lower ceiling. Knee walls not only need insulation, but also sheathing on the other side. This increases the performance of the insulation in the summer when attic tem­peratures soar. The sheathing should be sealed to keep air from moving through the insulation. Otherwise, the space acts like a chimney, with the rising and moving warm air negating the effect of the insulation. Bonus rooms may have doors to unconditioned portions of the attic used for storage. These doors should be insulated and sealed with weather-stripping. 

Since bonus rooms are so difficult to heat and cool, also be sure the room has as many other energy-effi­ciency features as possible, including sufficient ceiling insulation and well sealed double-glazed windows. 

Heating and air-conditioning contrac­tors frequently suggest adding more heating and cooling to the bonus room or zoning the heating and cooling sys­tem. That may be necessary, but the first step is to solve the insulation and airflow problems. It’s almost impossible for an air-conditioning system to cool this space if heat is pouring into the bonus room because of insufficient insulation or pene­trations through the floor and walls. 

Homeowners can make many of these improvements on their own, including sealing penetrations around plumbing and wiring, sheathing the knee walls, and sealing and insulating openings to unconditioned space. Jobs like blowing in additional insulation are best left to professionals. 

It is possible for your bonus room to be a comfortable space you can use year-round. A DigitalAir Homescan can pinpoint the reasons why your bonus room is difficult to heat or cool and suggest solutions. Call DigitalAir at 877-419-3738 or read about DigitalAir Homescan in the Residential section of the Jackson EMC website, 

Source: Jackson EMC

If you have a question, change of address, comment, home tip or would like to send Home Tips to your clients, send your letter to Home Tips, Christian Building Inspectors, Inc., 3697 Habersham Lane, Duluth, Georgia 30096. You can E-Mail your questions to us at We reserve the right to edit questions for length.

 Quote Of The Month

"It seems to me shallow and arrogant for any man in these times to claim he is completely self-made, that he owes all his success to his own unaided efforts. Many hands and hearts and minds generally contribute to anyone’s notable achievements.

Walt Disney

 A Tip Of The Hat To:

Jennifer & Shack Lewis

Re/Max Greater Atlanta

5163 Roswell Road

Atlanta, Georgia 30342

**** Thank You****