Choosing Sidewall Insulation10 December 2012
Three common sidewall insulation materials - fibreglass batts, blown cellulose and spray foam are compared by Jess Campbell, Dennis Brothers, Jim Donald and Gene Simpson of the National Poultry Technology Center at Auburn University, US.
Every winter when the weather gets cold we get lots of calls about sidewall insulation for poultry houses. Having
to turn the heat on (and up!) definitely brings to mind the potential benefits of insulation. Whether you are considering
installing wall insulation as a retrofit upgrade or improving new house construction insulation methods, it has
to be done the right the first time.
There are three sidewall insulation scenarios that we most frequently see: fibreglass batts, blown cellulose, and spray foam. This newsletter presents the facts about these three technologies as we have seen them in many working poultry farms, especially with the aid of thermal-imaging cameras.
How important can sidewall insulation be? Wall insulation directly affects fuel usage. If you get it wrong to begin with, it will affect the cost of operating the house for as long as the next 30 years. There are about 8,000 square feet of wall area in a 40-ft × 500-ft poultry house; which is a lot of area to lose heat through. The goal is to choose a wall insulation system that will insure tightness, have good R value to keep heat in the building, be reasonably priced, and deliver good value over a long enough expected lifetime. What insulation technology is best will vary from farm to farm, depending on the particular situation, including whether we are considering new construction or retrofit installations. What is best for a new house might not be ideal, or even feasible for a retrofit.
This photo shows a sidewall that was insulated with blown cellulose six years previously. The thermal image is almost like an X-ray showing how the cellulose has settled, leaving the top one-third of the wall basically un-insulated.
Fibreglass Batt Insulation
For new poultry house construction it is hard to beat a 3.5 inch R-11 or 5.5 inch R-19
batt (depending on wall cavity thickness), properly secured in place so that it won’t move over time. Batts plus a
good 6-mil poly vapour barrier installed over the posts or studs on the inside of the building and then covered with
OSB or plywood forms a very durable and well insulated wall. Our investigations have shown that these walls hold
up very well over time (see Figure 1 inside). A drawback with fibreglass is that while it works well in new applications
it can be difficult and costly to use in some retrofit applications.
For more information on use of fibreglass batting for retrofitting older poultry buildings, see Newsletter 46, Controlling Sidewall Energy Losses. For best results, the wall cavity must be totally filled with insulation. Never install a 3.5-inch batt in a 5.5-inch wall. Empty air space will allow the batt to shift and settle and provides little or no R-value. Installing a 6-mil or equivalent vapour barrier on the interior side of the insulation is imperative. Installing an exterior vapour barrier is not recommended because it will trap moisture in the wall cavity.
Blown Cellulose Wall Insulation
Blown cellulose was designed
mainly for overhead applications such as the attics of dropped ceiling houses. In vertical applications such as a wall panel, it has a tendency to settle over time, which leads to a loss of insulating value. For this reason, wall applications are typically not intended or recommended by manufacturers.
Prevention of settling has been attempted in many ways. Adding a glue binder with sufficient water to the mix and placing runs of horizontal blocking in the wall are two common practices. As you can see by Figure 2 inside, significant settling may occur over time even when blocking is used. Settling creates a serious heat loss issue and one that cannot be easily repaired. We would be very cautious to recommend the use of blown cellulose in vertical wall panels until we have sufficient data to be sure that the settling problem has been solved. If blown cellulose is used in a sidewall, a 6 mil vapour barrier must be installed before OSB or plywood is applied to the posts.
After eight years of service, settling in each of the blocked sections is evident – meaning significant insulating value has been lost.
Spray Foam Insulation
Closed-cell polyurethane spray foam, with an insulating value of about R-7 per inch, has been used in the poultry industry for about eight years in new or in retrofit applications where the use of fibreglass batts would be almost impossible due to high costs of carpentry or structural modifications to prepare the house for the batt installation. An older poultry house can be spray-foam transformed into a well-insulated and tight building within a matter of hours (see Figures 3 and 4 inside).
Figure 3 (above). North wall is spray foam over 2×6 lumber wall and south wall is spray foam over curtain.
Figure 4 (below) Sprayfoam is performing very well in this retrofit application after seven years.
The authors have done extensive field research on spray foam and its
value in retrofit applications. [See Newsletter 43 'Poultry House Energy Retrofits for Fuel & Cost Savings']. The
life expectancy of a typical spray foam application is seven to 10 years, depending on a wide range of variables.
The major possible drawback to spray foam is that it is susceptible to mechanical damage and damage by darkling beetles. In most applications, a higher density (6-10 lb) spray foam must be used in the lower 24 inches of the wall to keep the birds and beetles from damaging the foam. An alternative is to use lumber scrape boarding at the bottom of the wall. Considering all factors, spray foam is excellent in most wall retrofit applications if coupled with a good beetle control programme.
In new housing, the authors have seen this product being sprayed directly into wall cavities against the exterior metal, with no other insulation being used and no other vapour barrier installed, and then OSB or plywood being placed over the empty wall cavity. This is not equivalent to an R-19 fibreglass batt wall; and reports are that this system costs more to install than fibreglass. In addition, this kind of application could be subject over time to moisture accumulation and beetle damage which is difficult to monitor and remedy.
The Bottom Line
There are many pros and cons associated with different wall insulation
technologies for new poultry housing and for retrofits.
Getting the right sidewall insulation for your farm requires careful consideration of all the variables. But the benefits are clear. By getting it right and properly walling up we can improve the uniformity of the bird environment, save a significant amount on our fuel bill, and improve the structural integrity and longevity of our houses – all of which lead to long-term improvements in overall profitability.