Building Heat Loss

When Your Home is Loosing Heat, Where Does It Go?

by Don Ames


investigating heat loss

Every time I perform an energy audit, I get to investigate the reason why that home is experiencing building heat loss. Part of the audit is evaluating the home heating system. Without the mechanical system trying to heat or cool the building to maintain occupant comfort, there would be no such thing as building heat loss. Great amounts of time have been dedicated to the calculations and measurements involved to predict just how powerful a heating or cooling system needs to be to offset the recognized building heat loss. Your home needs a heating or cooling system because of building heat loss.

Heat flowing in to or out of our home is our largest energy consumer. Without building heat loss, we wouldn’t need a furnace at all. We almost wouldn’t need a power bill either. Of-course, a home without heat loss is a home without doors and windows and kids going in and out. Doesn’t work real well – just like ceiling radiant heat and baseboard heat didn’t work real well, especially where our power bills are concerned.

The need for heating or cooling is referred to as heating load. Take your climates worse day, when the temperature difference between outdoors and indoors is the greatest and calculate the number of BTU’s per hour needed to be added or taken away to keep the home comfortable, you have your heating load. And, that brings us back to building heat loss.

The are four things that determine just how many BTU’s are going to be involved in a buildings heating or cooling needs.

building heat loss

1.  Heat Transmission

This is the amount of heat that can pass through walls, ceilings, and floors. The heat passes through the building shell in three ways, Convection, Conduction, and radiation.

An example of Convection is the west wind or the ocean breeze. Get the air moving and you can have building heat loss by convection.  Another example is the cool night air against your skin – your skin looses heat by convection.

Example of Conduction is the heat that passes through solids simply because they are solid. This is one molecule passing heat to another because they are packed close together. The exterior siding of a home passes the heat to the studs they are nailed to which, in turn, pass the heat to the drywall and then to the inside of the home.

An example of radiation is the sun beating down on the big picture window or the energy auditors bald head. This type of heat transfer can even cause a sun burn.

2.  Air Leakage

Air leakage is simply the holes and gaps left by builders, electricians, plumbers, and heating contractors. Every time a contractor cut or drilled a hole in your home to install something, he  (or she ) probably left a hole. Doesn’t matter where it is, air is going to find the hole and flow from the area of high pressure to an area of low pressure.

Look under your kitchen sink, see where the drain pipe comes through the floor or wall – is the hole sealed or not?

3. Generated Heat

Generated heat needs to be considered and can vary greatly from home to home. Generated heat includes such things as household members, electronics, light bulbs, ovens and ranges, and the water heater that is in the closet.

Ever go to a party at a fairly small home where the whole senior class has gathered? Pretty soon, someone is running around opening up windows and doors. Yep, a teenage body can generate a lot of heat and increase the homes need for building heat loss.

solar heat gain

4. Solar Heat

This is an easy one, big picture window and the sunshine is streaming in, the room and whole house warms up requiring BTU’s to cool the home. Another example would be to stand beside an exterior wall that has been in the sun all day, the sun has now gone behind the distant hills but you can plainly feel the heat is still radiating off the wall.

The Advantage of Home Energy Audits

During an energy audit, my inspection will give me a pretty good idea of a homes building heat loss. With the blower door test I can determine the air leakage of the home and how great the need is for air sealing. The blower door determines how big a hole you have in your home.

By inspecting the level of insulation in the ceiling, walls, and floor, I can determine the level of heat transmission that is affecting the number of BTU’s it will take to heat or cool your home.

How To Use Building Heat Loss to Save Energy and Lower Your Power Bill.

With the knowledge of how your home losses and gains heat that, in turn, requires the furnace or air conditioner to kick on and start using energy and adding dollars to your utility bill, you have opportunity to address those building heat loss issues and begin to save.

3 Simple steps to address building heat loss.

1.  Energy audit.

Recommended is a professional energy audit by a certified home energy auditor. Next best is to perform a do-it-yourself energy audit. Remember, your looking for ways to control heat transmission and air leakage.

inspecting heat loss

2.  Air sealing.

Get out the caulk gun and the can of Great Stuff Insulating Foam. Remember the contractors, where did they cut or drill a hole in your home. Follow the wires, pipes, heating and ventilation ducts and see where they lead.

3. Insulation.

Check the attic, underfloor, and walls for insulation. Properly installed, it’s hard to have too much. Remember to air seal the ceiling and the floor before adding insulation. The air barrier needs to be tight before the insulation goes in.

By controlling building heat loss, your home will be more comfortable and will use less energy. The heating and cooling systems will simply not have to work so hard or so long to maintain the indoor air comfort you desire. Wouldn’t it be nice to have a home that is so energy efficient, that all you needed to do to maintain your comfort needs was to open or close a window.

Thanks for stopping by Detect Energy, hope you come back soon, but I won’t leave the light on for you…