An efficient heating system needs to be sized properly. Unfortunately, most residential contractors don’t take the time to do a Manual J Heat Loss Calculation or a Manual D Duct Design Calculation to make sure that the system is designed correctly. Improperly-sized systems will mean years of discomfort and inefficient energy utilization. It is good to ask questions. Ask your contractor, or their heating subcontractor, to provide you with copies of their calculations, then find an outside heating contractor to evaluate and verify the data given.
Bigger Is Not Better
Bigger is not better when it comes to the sizing an air conditioner. A properly-sized air conditioner will operate more efficiently and will not subject occupants to extreme temperature changes between too cold and too warm. It is so easy to be sold an air conditioner with a larger capacity than is necessary, as we tend to equate “big” with “better”. In reality, a properly-sized air conditioner running over a longer period of time will operate more efficiently, and will off more comfortable temperatures than one that turns on and off all the time. If you have an air conditioner that does this type of “short cycling”, then chances are it is oversized relative to your space.
Think System, Not Furnace
Your heating system is more than just your furnace. It includes the furnace, filtration, duct system, and the envelope of the house. No matter how efficient a furnace is, if the ducts and/or your home leaks, you are wasting energy.
Duct Tape: Not for Ducts
In older homes, air ducts were sealed with duct tape. Like most tapes, after a few years the adhesive wears out and you no longer have a sealed duct system. To make matters worse, in some homes nothing but tape was used to seal the duct system. The ducts are the delivery system for conditioned air throughout your home. When we test duct systems we typically find 30-50% leakage, meaning that only a portion of the heated or cooled air the homeowner pays for is actually being delivered to the home, and the rest is leaking out into the attic, walls, or crawlspace. Your ducts should be sealed professionally and then pressure tested to confirm that duct leakage is 6% or less than total system airflow. Many heating contractors do not have the training or experience to test and seal ducts, however the leaders in the field do.
Duct leakage is more than wasteful – it can also can create pressure imbalances in your home. Leaky ductwork can draw pollutants into your home and can cause back drafting of indoor combustion appliances. To avoid these issues, ducts needs to be tested and sealed by a professional.
During the construction process, a vast array of contaminants and objects have been found within the brand new ductwork in new homes, such as sawdust, soda cans, food bags, water, and other construction debris. To prevent further contamination, once the duct is installed it should be sealed to prevent the entry of all the things homeowners don’t want to be breathing for the next 30 years.
Most filters were designed to protect the furnace from debris; they were not designed to protect our lungs from fine particulates. When looking at your filter, if you can see your hand through it, it was designed to protect your furnace, not to filter particulates to protect your lungs. Have your HVAC contractor install an easy-to-access, disposable, 4-6 inch, MERV 13 or better filter. Cutting edge, expensive, UV filtration equipment is not necessary in many cases. Ask questions – don’t just accept the default.
Many homeowners experience excessive noise with some of their large appliances. Believe it or not, kitchen range hoods do not have to be noisy. You can now purchase remotely-located fans that can be placed in the attic that will be very quiet. As with many alternatives, if you don’t ask, you won’t be offered this option. For bathroom fans, Panasonic has a terrific line of very quiet bathroom fans called “Whisper Quiet”.
Don’t Mistake Leakage for Ventilation – Ventilation Air in a Home is Important
Pollutants, humidity, odors, and chemical compounds will accumulate in a home that is not ventilated properly. Homes used to be so leaky that getting enough ventilation air was never a problem. Though you may hear contractors say a home can be “too tight”, a better approach is to “seal it tight, then ventilate right”. Rather than leaving ventilation to chance penetrations in a structure, all penetrations should be tightly sealed and the home should be pressure tested with a device called a blower door to confirm that proper ventilation rates are achieved.
Insulation, done well, is perhaps the single most important, and least expensive upgrade we can make to make a home energy efficient. Unfortunately, oftentimes insulation is not done well. There is a myriad of choices and approaches, including fiberglass batts, dense-pack or loose-fill cellulose, and closed cell foam insulation. Closed cell foam insulation is expensive but ideal because it provides both a thermal barrier and an air barrier. Insulation is both an art and a science. The difference in price between a quality insulator and low-ball firm is minimal when you consider the impact a poorly done insulation job will have on the long-term energy utilization of a home. Start researching insulation solutions early in your remodeling or construction project. It may even help to have an independent third party come in and verify that the insulation was properly installed. Also, prior to insulation the home should be pressure tested, air leaks in the building envelope should be identified, and efforts should be made to seal all gaps around plumbing and electrical penetrations between the attic, garage, crawlspace, and the home.
Improving the insulation in an attic is only part of the story. It is important to seal up air leaks between the attic and living space before adding insulation.
Recessed Lighting Fixtures
This is a popular feature that also poses a huge air leakage pathway between the home and the attic. Air sealed canister light fixtures that are IC (Insulation Contract) rated should be used, but unfortunately many contractors don’t consider using them because they are more expensive or are unaware of them.
Indoor Pressure Imbalances
Kitchen range hoods, indoor clothes dryers, and bathroom exhaust fans all contain powerful fans that can cause a tightly sealed home to become slightly depressurized. This can create a safety issue when the negative pressure in the home overpowers the natural drafting of indoor combustion appliances, such as furnaces or fireplaces, and can lead to the accumulation of toxic carbon monoxide, a byproduct of combustion, in the living areas of the home. If your home has indoor combustion appliances, then a worst case depressurization evaluation of the home is advised.
Out of sight is out of mind, yet these overlooked areas of the home have a huge impact on the quality of air in a home. Due to some basic physics and a phenomenon called “the stack effect”, hot air rising through the structure draws cool air into the home from the crawlspace. It is estimated that 30% of a home’s indoor air comes from the dusty, and frequently odiferous, crawlspace. If your home has a crawlspace, it should be designed for easy access for inspection and maintenance. For new construction, there is no excuse for a crawlspace not to be well lit, dry, clean, and free of debris and dirt. It should be covered with a wall-to-wall, sealed vapor barrier. If you have a finished basement, then exterior water proofing, insulation, and drainage systems are important to be designed and implemented well.