AHP Project, Day 7

Note: the following is not a comprehensive listing of all the details involved in a full audit.  It's meant to be a general description of the process so please don't think that you can read this and do one yourself.  Your and the homeowners' safety requires a full Building Performance training, at a minimum.



John and Jane are delightful. Pretty much your ideal clients: interested in not just the audit findings but the process itself, close by but not in the way, curious and open to learning about efficiency and building science, and John makes good coffee. Sweet. After getting a copy of their utility bill history, something I prefer to have beforehand but was unavailable til today, and a friendly meeting to check in about any issues and to let John know the logistics of the day, we were ready. Start my personal CO meter and clip it to my belt, make sure I have spare rechargeable batteries for everything, clip blank forms to the clipboard, turn my phone ringer down, and think through the day in my mind. Move all the equipment onto a pad in the living room and decide we will wear socks instead of booties over our shoes.  My helper for the day is Dilip Sinha, an intern breaking in to the business. Though mentoring can be time consuming, it's also gratifying and a way to give back to those who helped me when I was just beginning.

At 8:30, it's still brisk out and warm inside so a quick tour through the house with the IR camera clearly shows a few insulation problems. The ones in the attic, R19 with the normal mediocre installation, should be easy to fix. The ones in the walls are what they are, impossible to repair without serious demolition. The floor is uninsulated. Even before we set up the blower door, it's easy to see the rays of cold air streaming in under the french door shoes and along some of the baseboards so I know that will be even more obvious later.

First, safety checks and Worst Case CAZ (combustion air zone) test. The FAU (forced air unit) is a 10 year old, 80% Carrier downdraft with powered vent. It's big. 93Kbtu output. Way oversized for this 2200 square foot house and a perfect example of how we used to think: the solution to almost everything is a bigger system. It shares a vent with a standard 40 gallon DHW (domestic hot water heater), then passes up through the attic and out the roof. In this house, both are in a closet in the middle of the house, behind double hollow core doors with no weatherstripping. Further, there is a 4X14 vent in the ceiling of the closet, no vents in the floor, and a 2X14 vent into the living space in each door. Two immediate problems: the total size of the air vents into the closet is considerably undersized for combustion air for both appliances and much of the combustion air is drawn from inside the house.

When both appliances are off, air from inside the house flows through the door vents and up into the attic through the ceiling vent. A quick peak behind a receptacle cover plate shows no insulation in the walls between the closet and the adjacent bedrooms.  And later, when the attic has warmed up in the sun, the blower door shows warm attic air being drawn into a bathroom next to the FAU closet *under* the wall between them! Common practice 50 years ago but poor from an energy and indoor air quality viewpoint. So the tests: the FAU passes easily since the flue has an excellent draft and the DHW would pass except that it has a flat plate under the draft hood, meant to reduce standby losses, that causes significant spillage of combustion gases. The whole concept of a DHW and an FAU in an uninsulated, poorly vented closet in the middle of the house is a poor one and is no longer even legal.
One final thing: the entire return duct system in the attic has no insulation at all. Nearly 100 square feet of duct surface exposed in the attic with an R value of 0. The heat loss or gain is substantial. All this goes into the report.

Next, the blower door test. Since all the exterior doors are french doors, including the front door, I decide to put the blower door into the door to the garage and open the main garage door. Start the pressure at -10 pascals, make one more trip through the house to make sure the wood stove inlet is closed tightly (a messy disaster if it's not) and to check all windows and doors, then run the pressure up to -50 pascals. 3365 cfm50. Moderately leaky and about what I'd expect for a 40 year old house. Drop the pressure back down to -20 and take John on a tour through his home with the IR camera. There's nothing quite like watching a homeowner clearly see where air is streaming in under baseboards, around sink plumbing in the wall, recessed ceiling fixtures, and through switches and receptacles. It's difficult to say no to air sealing the shell when the air infiltration is right there in full color. A moment of mea culpa: an unusual cold area in a bath, while touring with the IR camera, shows that I missed a window being open a crack behind a curtain. At least I caught it and redoing the blower door test yields a new and corrected number of  3110 cfm50. Check and recheck.

Now for the duct test.  John has replaced the ducts a few years ago because of rodent damage so I'm hoping for a low number and the test shows 255 cfm50. This calculates to 13% leakage, which is fairly good when I calculate for the oversized furnace which should have 2000 cfm of flow. But the true measurement of the flow with the furnace fan on shows 1050 cfm, only half what it should be. This is another all too common problem. Undersized ducts that are partially kinked somewhere in their length, creating enough back pressure to cut the flow in half. Using the true airflow rather than the 'should be' airflow shows a 24% duct leakage, quite significant. One thing I noticed, within a minute of the FAU shutting off, the floor registers showed up as blue or cold, indicating that crawlspace air was being drawn into the leaky ducts by the normal stack effect.Too bad John's paid to have his ducts replaced already because they need some serious attention. One final point to notice: the high water lines on the pier blocks in the crawlspace. Wow, there's some serious flooding during the winter. In fact, and this photo doesn't show it well, it touches the bottom of the supply plenum in the distance.

Last, Dilip does a full take-off of the house, measuring each of the outside walls and windows. Tomorrow, I'll enter all this information into EnergyPro software and model John and Jane's house. With a few tweaks and adjustments, it should tell me roughly how much each of the upgrade features I plan on suggesting to John and Jane will reduce their utility usage.

Five hours later, we're packing up the final bits. Tomorrow, I have the day blocked off to write John and Jane's report. I have found, from talking with other Home Performance Contractors, that I'm slower than most when it comes to auditing and writing up the report. So be it. My belief: it should take as long as it takes to do it right.