How many times have you started into a project and had to stop and redo some steps? How many times have you finished and then realized that you had extra parts? So what do we do?
We go back and read the directions! The manual! It is so common there are several acronyms for reading the manual. Directions written by the manufacturer serve several purposes. Some of the cynics around, including myself, realize there is a bit of self promotion and defense in these instructions. We should also realize that the manufacturer has probably tried to put a few of these together. He may be sharing his wheel with us, so we don’t have to invent it ourselves.
Most importantly, the manufacturer knows how the piece was engineered. The directions take that knowledge and apply it to how the equipment is set up, used or installed. Equipment changes over time. New features are added, materials change and the way it used to be done, is not a good idea. So, read the manual.
See the attic rafters above. This is the top of a vaulted ceiling, and the insulator has properly placed an insulation ruler. In a few weeks, blown insulation will be installed and the tech needs to measure how much. The use of the ruler and blowing the insulation level are two of the biggest helps to installing blown attic insulation. And Yes! They are in the manual!
The choice of this picture isn’t the insulation ruler, it is the nail grid on the ceiling joists. Machine applied in the truss shop, it is fast easy and effective. Notice the upper right hand corner of the grid. That is a sharp edge. Be careful, it will cut things. Hands, pants, shoe tops. Yes! All of those and don’t ask me how I know that! My wife makes me carry a first aid kit with lots of bandaids for a reason.
The house I finished a rating on yesterday had these nail grids on the floor trusses between the basement and the main floor. It also had the HVAC Ducts run between and through the trusses. The contractor on this job uses sheet metal supply plenums and take offs. He uses the flex duct to form the return air side of his duct system. Yes! Flex duct gets torn also. Especially with a nail grid.
Two weeks ago, I tested this home. The duct system was very leaky. According to the Quality Installation Verification Standard written by the Air Conditioning Contractors of America, it was leaking 100%. Wow! I’ve tested this contractors work before. He always does better than this. So I ran the test again. Checked my set up. No change. So I called him. Shon came right out. He looked over the system and immediately saw a couple of problems. Including this section of flex duct.
Now, two weeks later, his crew has reworked their ducts. I’m back to test it again. I run the same test and scratch my head. What leakage – I can get the readings right. The picture left shows no air flow, on the right side, and a very low pressure difference, on the left side of my manometer. The procedure is to have the Blower Door depressurized the house. Then you depressurized the duct system with the duct blaster to equalize the pressure. When the pressure difference comes down to Zero, you read the leakage to the outside of the house.
So I checked my set up and tested again. Still no readings. So …. I read the manual. In this case a Field Guide from the Quality Folks at my RESNET Provider and The Energy Conservatory that makes my equipment. I read it twice. Then it hit me. This line: Check the duct pressure. A negative duct pressure indicates leakage to the outside. If the duct pressure measure Zero with the Blower Door running, then the leakage to outside is Zero CFM.
As you can guess, the leaks when I tested two week previous prevented this result. What changed? The crew had found a small tear in the flex from one of the nail grids. Did you see it in the picture up above? I can see it because I know it is there. So I enhanced the image and that one is posted below. To get around all the reflections of the silver colored coating, I placed a piece of white plastic inside the flex so the hole would show.
So reading those pesky directions on a test that I routinely run, gets me the right answer. What about the Heating and Air Contractor. Shon does good work on his jobs, because he follows the professional guidelines and tests his work. In this case he knew the test, he knew what it meant and immediately saw how to fix it. What would have been the result if this basement had been finished out and then he had to remove drywall to fix it?
Why is ZERO duct leakage to the outside important? I don’t want to pay money to heat or cool the outside. If your ducts leak very much to the outside or don’t distribute the air properly, then you are spending more than you need to. Installing ducts with no leakage to the outside in a new home is an easy process for the contractor. It give the home owner a much better value.
Yes! I have found duct leakage behind drywall also. Here is an infrared image of a finished basement ceiling. The homeowners complaint is there is no air flow into his bedroom and it is cold in the winter and hot in the summer. To get this image I turned the furnace up to about 80° F. It was usually about 73° F. I stretched out on the basement floor and waiting for the heat from the furnace to leak into the cavity between the main floor and the basement ceiling. In a couple of minutes I had heat patterns showing. You can see where the duct is running up and down next to the floor joist. Interesting heat spot to the right next to the other joist. Also across the joist and over to the left joist. So we are seeing the duct and hot spots on each side 16 inches away. Lots of lost heat not getting into his bedroom.
The home with the infrared picture had the leaks on the supply side of the duct system. The one I tested yesterday had the leaks fixed on the return side. I could not have tested with the infrared in the same way yesterday.
So, on this Independence Day, we celebrate! We celebrate our freedom to be in a business we love, where we can do some good, and make a difference. And yes, where we can make a living for our families. We also celebrate the freedom to know our job, to continue to learn as things change and to utilize our professional standards to keep our customers happy and satisfied.
Have a Safe and Happy 4th of July!
Credits: Photos, myself. Insulation Ruler – Northstar Comfort Systems Install. Duct system install tested yesterday with no leakage to the outside — Shon Peterman and Midwest Mechanical. The audit providing the infrared image, my customer Craig. The new home tested yesterday courtesy of Sharon and Wade Wilkinson of GJ Gardner Homes. It is in Fontana.