The nice thing about building a custom home that is designed just for you, is that you have options that a lot of spec builders don’t offer when it comes to the stuff you can’t see, such as the insulation and the sheeting used on the walls and roof. So, with the importance of energy efficient homes in the world that we are living in, I thought I would spend some time explaining what we used to do versus what we recommend now.
The basic insulation that we have seen in our area over the last several decades has been an R13 batt insulation installed in the 2x4 exterior wall cavities, then after sheetrock, we would blow in an R30 or R39 insulation on top of the sheetrock in the attic. While this is far better than the newspaper that they put in the wall cavities back in the 50’s, if they put anything in them at all, it doesn’t hold a candle to what we can do now with other options. Some have and still use 2x6 exterior walls in order to get a better R-Value in the walls and still use batt insulation. This allows you use an R19 batt in the walls instead of an R13, which helps. Just remember, even though it doesn’t seem like a lot, you will lose 2” of interior space around the exterior of the house when you do this. In most areas in the Springfield Metro area, you can still use R13 batt R39 Blow insulation method, but due to the energy codes that are being adopted, this will soon be a thing of the past.
About twenty years ago, we started using house wrap to help keep water and air from entering the house past the siding or brick. This made houses with batt and blow type insulation less drafty, which increased the efficiency of the home, since air will move through fiberglass insulation. Additionally, the house wrap would allow moisture vapor out of the house which helped to keep mold and mildew from forming. For a short time in the 1990’s, some builders were putting plastic sheeting between the studs and the sheetrock to help with air infiltration, but because it left no way for moisture vapor to escape, they started having moisture problems and stopped the practice.
We now have a product available to us that is sheeting, and house wrap all in one. It is called Zip board and if you drive around a subdivision where houses are being framed, you have probably seen the green colored OSB on the exterior of some of the houses with black tape on the seams. That is the Zip system. The advantage of using Zip is that you don’t have to worry about the house wrap getting damaged while waiting for siding or brick and you’re much less likely to have a future window leaks because of the way the system works. It is more expensive that standard OSB and House Wrap, but it may be worth the extra cost, knowing it is a superior system and will help insure your custom home is built the best way possible.
Foam insulation has been around for a while but has gotten popular over the past few years in custom homes. There are two basic types of foam insulation, open cell foam and closed cell foam. Open cell foam is most common in residential construction. It is more flexible and expands to be thicker than closed cell. It is typically sprayed in the 2x4 wall cavity and about 6 inches thick on top of the sheetrock or along the rafters in the attic at the roof line depending on method being using for installation. Closed cell foam is more commonly used in commercial metal buildings, pole barns, or metal shop buildings. The nice thing about closed cell is it helps to shed water and adds to the structural strength of a corrugated metal building, but it is typically more expensive than open cell foam.
It has been my experience that open cell foam is the most efficient way to insulate your home, but there are a few things to consider. There are more up-front costs associated with it than just the upgrade to this type of insulation. In combination with the Zip system, Foam expands and fills all the tiny holes and cracks that are common in a wood frame house, which is great! With that tightness, however, the air in your home will become stale if you don’t vent the house mechanically. We do this by using an ERV (Energy Recovery Ventilator). An ERV removes stale and humid air to the exterior of the home and brings in and conditions fresh air from outside. This helps to prevent moisture problems and helps with allergens that are floating around in the outside air. Typically, with a well-designed HVAC system along with the use of an ERV, the air inside of your custom home will be fresher than the air outside. This is why so many people are using fewer operating windows, opting instead for picture windows in most rooms of their homes. Incidentally, the lower cost window package helps offset some of the cost of the ERV. As of the time that I am writing this, the cost of an ERV is around $2700 installed.
Using open Cell Foam, Zip Board on the exterior, and adding an ERV will increase the up front cost to your custom home, but if you are planning on staying in the home for more than a handful of years, the energy savings will help you recover the additional cost of construction. For a more detailed description of how we can help you build your next energy-efficient custom home, give us your information on our Contact page or give us a call at 417-536-1448. Thanks for reading.
By Ryan Green
First Choice Custom Homes