December 14, 2018

To tighten or not to tighten…this is some question poultry producers may ask as their production facilities get some age on them. For new houses, this better be a no brainer; if a new house isn’t tight, you need to have a frank discussion with the construction engineer. But for older houses, we need to ask ourselves what the payback is relative to the geographic climate conditions (although weather has been unpredictable – on November 29, I was talking to a customer near Charlotte, NC and his thermometer was in the 20° range. At the same time my temp near Gettysburg, PA was in the mid 30’s), how long the house will be in operation, and what the cost benefit is. In this article, we will look at the benefit part, only from a house tightness perspective, not an insulation value perspective.

First, does my house pass the Tight Test (TT)? The TT is a simple measurement to determine how tight my house is when everything is closed (inlets, doors, attic inlets, etc) and the equivalent of 1 cfm/ ft² fan capacity is operating. If the static pressure (SP) is at least 0.15”, I have a pretty tight house. If the SP is not at least 0.15”, then either my house is loose, and/or my fans are not moving the air capacity I think they are. Let’s assume my fans are ok. The table below calculates how much leaking I have in my house through cracks in doors, loose inlets, leaking sill plates, etc, etc. Even at a TT of 0.15” SP, I have 11 ft² of cracks or leak in my 20,000 ft² house. Notice, new houses can have SP reading of over 0.25” with the TT. So, a new 20,000 ft² house with a TT of 0.25” SP has about 6 ft² of cracks or leaks. Unfortunately, a lot of older houses have low SP values when using the TT. Note, a house with a SP of 0.05” TT has 35 ft² of cracks or leaks. The first advantage to a tight house in cold weather is removing drafts on birds. Look at the pictures below. Smoke generators show leaks in sill plates, end doors, leaky fan shutters, holes in walls, etc. When this happens, we have 3 unwanted problems –
1. We chill birds by creating drafts with cold air directly in
the growing area
2. We dump cold moist air directly on the floor creating
wet areas and increasing house humidity
3. We increase the need for artificial heat to reduce
humidity levels drying litter

The second advantage to a tight house in cold weather is the ability to control the incoming air and direct it where we want it – to be able to take advantage of preheating the incoming cold air with heat rising to the ceiling and to be able to remove moisture from the house. By controlling the incoming air, I can achieve the opposite of the three items listed above.
1. Eliminate cold drafts in the growing area
2. Bring cold air in and direct it along the ceiling to
preheat it, allowing it to expand and carry moisture, to
be able to reduce humidity levels
3. Reduce the need for artificial heat, lower humidity levels
and keep floor dry

By identifying whether I have a loose house or not, by performing the TT and then identifying where the leaks are, I can decide the best method to tighten the house and then determine if it is the right thing to do. Depending on outside temperatures, the reduction in fuel use between a 0.05” SP and a 0.15” SP house can be as much as 50%. I can easily calculate that return after I know what my cost to tighten is. The bonus will be in how much better my birds perform because I have improved their environment in cold weather. (Future articles will address how much heat I lose through poor insulation, as well as how house tightness impacts air speed in tunnel applications.)


For More Information:


John Menges

« Back