How can you tell how leaky your home is, or how should your builder commission your house and qualify it for being tight? The answer, according to the latest research in building science, is through the use of a Blower Door test. Think of this as a Quality Assurance test for your home. For a basic understanding of how pressure testing is done, see my last article (How Leaky are your Air Ducts?). A “blower door” consists of a powerful variable-speed fan, mounted in an adjustable panel that temporarily fits in a doorway, that is used to move air through the building in a controlled and precise fashion. Pressure gauges connected to the fan measure the rate of airflow required to maintain the building at a certain pressure. The standard pressure used to test homes is 50 Pascals. This not a lot of pressure. In fact, this suction pressure would pull water up a soda straw only about one-quarter inch. So it’s not like we’re doing a wind tunnel test, and Fluffy the cat is not going to be sucked into an industrial turbo fan. But it is a very precise fan. We’ll use the same digital micro manometer (see the Duct article for an explanation) to tell when the variable-speed fan has created a 50 Pascal pressure differential between the inside of the home and the external environment. This is called the CFM50 test. Once we achieve the required pressure differential, our computer tells us how much air (measured in Cubic Feet per Minute or CFM) is moving out of the home. This is the gold-standard test for comparing homes in terms of air tightness. There are standards for best practices in this test, and we can compare your home to what is considered the best achievable result.

Once we know that the home is not as air tight as it should be, we can use this same equipment to determine where the major air leak locations are. For example, to determine whether the master bedroom suite is the culprit we would shut that door and run our CFM50 test on the home. We would then check for air movement under or around the master bedroom door. If that bedroom is the cause of major leaks we will find air movement. If that bedroom is sealed well, we will not. We can use this same technique with any space in the home which can be closed off. We would also use chemical smoke pencils or “puffers” to find where there is air movement. Many of the leaky areas you will actually be able to feel the air movement with your hand.

Of course once we can determine that a home (newly constructed or of any age) is leaky, and once we locate the major leaks, the next step is to seal the leaks. This is the easy part, and we can actually run the CFM50 test after each major leak source is corrected in order to see the magnitude of that specific leak source on the test results. If we build your new home you don’t have to see any of this happening. We’ll give you a copy of our final test report documenting the fact that you are receiving a state-of-the-art home in terms of air tightness.

There is no other way or method to determine the quality of the construction (or the builder) with regard to air leaks than the Blower Door test. If building a new home, insist on it. If doing a major remodel, insist on it. If you are concerned about your current home, are unhappy with the air quality or believe your utility bills to be too high, you should have this type of testing done. If you want to pursue any of these issues, contact me using the link below.

To comment on this article, please contact dkoloski@pbsbuilthomes.com

The quality of your HVAC ductwork is something that can actually be measured and quantified. This article will explain why and how this is done. Leaky ductwork hurts your household budget, and actually puts the health and safety of your family at risk. Read on to understand how this all works. By the time you are done reading this article, you will probably understand this topic better than the builder who constructed your current home.

Your heating and cooling system includes a blower fan which pushes air into the supply ductwork, and pulls air through the return ductwork. Ideally, your ductwork system is perfectly sealed, so that the only air pulled by the blower fan is the air coming into the return grilles, and the only air coming out of the supply grilles is coming directly from the blower fan. This does not happen in your, or in any, home. All ducts have leaks, and a great duct system has no more than 5% leakage. Your home probably has 20% to 40% leakage. If you do not have a very high-efficiency heating system (if your home is more than a few years old, you don’t), you may be wasting up to half of your heating dollars trying to heat your attic. That sounds alarmist, but there are documented cases in which this is true.

So how do you tell if you have a tight ductwork system? With the use of a digital micro manometer and a calibrated fan. A manometer is a very precise scientific instrument which measures air pressure. The unit of measure for pressure for our purposes is the Pascal. Without turning this into a high school science class, just understand that atmospheric pressure at sea level is 14.7 pounds per square inch, and that there are about 100,000 Pascals in one atmosphere. So a Pascal is a pretty precise measurement unit for air pressure. A calibrated fan is a very precise fan which can tell us how much air it is moving. The unit of measure for the fan is CFM, or Cubic Feet per Minute. Let’s talk about how this all works.

When your blower fan is running, it is creating positive pressure in your supply ducts. Imagine that all your supply air registers are closed and sealed tight. The blower fan would be trying to push air into your ductwork, but the air would have nowhere to go. It would be like blowing up a balloon. Except that your supply ducts are like a balloon with a pinhole. If the pinhole is small your ducts are tight. If the hole is large, or if you have many holes, your ducts are leaky. When your fan comes on, it is blowing some of that conditioned air out through the holes and leaks, into unconditioned spaces (like your attic). The blower fan is creating positive pressure inside your supply ducts. In like manner, if you have holes and leaks in your return ductwork the blower fan is sucking air from the unconditioned spaces surrounding your return ductwork. The blower fan is creating negative pressure inside the return ducts. Air always moves from an area of high pressure to an area of lower pressure.

Now imagine that we could seal all the registers in your HVAC system, except one. Now imagine that we can temporarily install a very scientific, precise fan at the open register. We then could use that precise fan to blow air into the ductwork system. The sealed ducts are like that balloon, right? Unfortunately, your ducts are like the balloon with pinholes, so instead of trying to push air into a duct system with nowhere for the air to go, instead the forced air is going out through those holes and leaks. It is not going out through the other registers because we sealed them all very tightly. Now the fan is calibrated, and a digital readout tells us how many CFM (Cubic Feet per Minute) are going through the fan, and of course therefore through the holes and leaks in your ductwork (because unlike the balloon, the ductwork is not going to expand, the air has nowhere to go but out through the holes and leaks). We use the digital micro manometer to measure the difference in air pressure between the interior of the duct and the surrounding air. In current building science practice, we measure something called CFM25. We pressurize the ductwork to 25 Pascals relative to the surrounding air, which we measure with the manometer, and then read how many CFM are being pushed with the calibrated fan in order to achieve this pressure difference. So if the ductwork is very tight, we would need very little air (CFM) to achieve a pressure equal to 25 Pascals. If the ductwork is extremely leaky, we would need a lot of forced air (high CFM). (If the ductwork were completely open, the fan would never be able to push enough air to achieve a 25 Pascal pressure difference because it would be trying to pressurize the completely open duct relative to the atmosphere). We then compare the CFM reading to the rated CFM for your HVAC system’s blower fan. This is how we calculate the percent leakage in your ductwork. We do this test on every home we build.

This article barely touched on a very important topic, but at least you now know two very important facts. One, it is important to know how leaky (not if. That’s a given) your HVAC system is. Two, you now know that the leakiness can be measured and quantified. Of course, we can also do this test in your present home. More importantly, leaky ducts can be corrected. (Just don’t use common gray duct tape to do it, but that’s another article). We can also test the leakage of an entire home’s enclosure to quantify how leaky an entire home is. We can also test for pressure differences between different rooms in a home. You care about this test if you have hot or cold areas or rooms in your home. These topics will be subjects for future articles.

So if your home is relatively new, or if you are currently having a new home built, ask your builder what your CFM25 reading was, or what standard he is building to. It is in your family’s best comfort and health interests to do this. If you are thinking about building a new home, and you care about air quality and utility bills, give us a call.

To comment on this article, please contact dkoloski@pbsbuilthomes.com

If you answered “Yes !” to any of the above questions, then you should care about how your home was engineered, or more likely how it was not.

Homebuilding is a tradition as old as man himself, and home builders by and large are a very trustworthy lot who care about building your home as well as they know how to build it. And there’s the rub. Do you have faith that your homebuilder is up to date on the latest research regarding building materials, construction techniques and building science? When you ask rational and logical questions about their methods, do you get answers like “We’ve always done it this way”, or “This is how I was taught how to build a home”? When your builder tells you that he has 10 (or 20 or 30 or 40) years experience building homes, do you ever wonder whether he learned much beyond the first five years? Or is he now building the same way he did 5 (or 15 or 25 or 35) years ago? There is certainly value in tradition, but not when it substitutes for a real understanding of why things are done a certain way, and more importantly why those ways need to change when building materials change, or when research uncovers the reason why water finds itself in a building structure and causes mold (to cite just one timely building issue).

We intend to lead a paradigm shift in how homes are designed and constructed in our geographical area. We will utilize system thinking. We will take advantage of the latest research in residential construction. We will share the latest thinking with anyone visiting this website, by writing frequently in this section of our site about topics of interest to homebuyers. The first such article is about HVAC ductwork testing. It is almost certainly true that you are throwing money away because your ducts are leaky (Got your interest? Now go read the article). We actually test our homes as they are constructed, in order to assure a non-leaky HVAC system and a non-leaky exterior enclosure.

This introduction, as well as future writing, will no doubt cause friction among the home building community. That’s OK, because from friction comes both heat and light. Perhaps even the light of understanding.

You may wonder why we would openly post all this information on our website, for not only potential homebuyers but also other builders to read. Surely if we “tell it like it is” then in time they will know everything that we know, and we will no longer have the competitive advantage of having done all this research. There are a number of reasons. Most importantly, we think that everyone deserves to own the best home possible. Even if we do not build your next home, we want you to be able to ask good questions so that your builder gives you a home that is tight, well insulated, durable, safe, well ventilated, comfortable year-round and with the lowest operating costs possible. Second, we openly admit that we don’t know everything, but we know that we will continuously improve, so that we stay “ahead of the curve” and other builders with regard to the latest research, materials and techniques. (We certainly don’t claim to be know-it-alls, and we often will not have a ready answer for your questions, but we will know exactly where to go for the best answers and we will know the most knowledgeable people in this industry). Even if you do not favor us with a contract to build your next home, at least we will believe that our efforts may result in a better home than you otherwise could have expected. Unfortunately, we also believe many builders will not want to change, or will not be able to adapt to new learning. You will be able to recognize these builders. They will be the ones who say “We’ve always done it this way.”

To comment on this article, please contact dkoloski@pbsbuilthomes.com