Arizona Summers can be brutal throughout the months of May through October according to abc15. With the ideal temperature of the inside of the house being 73 degrees, and the outside reaching 115 degrees its paramount that the design, quality and material going into your home addition are the best. Below I’m going to discuss affordable ways and small things you can do to make sure your new home addition is built with energy efficiency, and quality in mind.
First let’s start with the design / framing of the build or what I refer to as the skeleton of the house. According to Houzz, when using a traditional 2×4 wall 16” on center, your total R value of that wall isn’t R-19 its actually closer to a R15. Although the insulation installed in that wall is a minimum of R19 that doesn’t mean the wall itself is a R19 wall and here’s why. Every 2×4 piece of wood doesn’t have a R19 value it only has a R value of 4.4. Thermal bridge meaning an area or component of an object which has higher thermal conductivity than the surrounding materials, creating a path of least resistance for heat transfer. IF you look at the picture below, you see that every 16 inches there is a thermal bridge from the exterior to the interior because the wood only has a R value of 4.4. So, when you calculate a total R value of a wall including that thermal bridge it only equals to a R15. Here’s how you can achieve a better insulation and less thermal bridging affordable. Instead of using the traditional 2×4 wall 16 on center, use a wall system that consists of 2×6 framing members spaced at 24 inches on center. When you use a 2×6 wall you have less thermal bridging because you are using less studs. So, when you’re working with your architect you can utilize a 2×6 wall rather than a 2×4 wall because with a 5.5” thick wall you can use even more insulation and have less thermal bridging.
Continuing on with design and build, you have to think about what your exterior siding will be. Generally, in Mesa Arizona, home owners usually go with a 3-coat stucco finish. When you know how the builder is achieving their sheer strength either with a sheathing and nailing method or using diagonal metal bracing. If they are using a sheathing method, instead of using ordinary sheathing like ½” plywood or ½” osb you can purchase insulated sheathing that ranges from R3-R12. So now you can still use a 2×4 wall system but you significantly decrease that thermal bridge of the 2×4 studs by installing exterior insulation. When achieving shear strength through diagonal metal bracing, you can install thicker Polyiso which is a closed cell foam ridged foam board. According to National Roofing Contractors Association a 2 inch Polyiso board achieves a R-!0 value. Now you couple a 2” thick polyiso with a 2×4 wall and you achieve an R25+ wall. So, as you see, combining a desired wall system with the correct exterior siding and you have a well-insulated wall.
Moving on, sometimes homeowners don’t have the money to build a 2×6 wall with 2” Z- sheathing insulated sheathing. So, what do we do? We take a small budget and maximize our quality of a build through water and air tightness. Typically, when home owners are on a budget their home addition will look like a 2×4 wall, osb sheathing, a Tyvek house wrap and a finished t1-11 exterior siding. Let’s take the above wall system and make it the best we can. First it starts with the mud sill or the pressure treated plate that touches the concrete. You will want to install a thick bead of a polyurethane concrete sealant underneath the mud sill. Once the mud sill is bolted on you will want to install another bead of polyurethane sealant where the edge of the 2×4 hits the concrete or stem wall.so now we have 2 beads of sealant protecting our house from critters, water and air from penetrating. When installing the sheathing, you can really make your house last longer by installing a pressure treated plywood on the first 2 feet of the house up from the ground. This part of the house gets the most water splatter. When water hits your roof and rolls off, the water hits the ground typically 1-2 feet away and when it does hit the ground the water splashes onto our buildings. So, by having a pressure treated plywood installed on the bottom half of our building it created a stronger resistance to water damage, termite damage and decay. Now whether you install a pressure treated piece of plywood or just your regular sheathing you will want to install another bead of caulk where the sheathing meets the stem wall. By installing that extra bead of polyurethane caulk, we now have 3 layers of high quality protection from air leaking out, water and critters getting in.
let’s say you install regular sheathing and no pressure treated stuff. To make sure your house has more of an air tight seal to keep the cool air from inside the building getting out, you can install HVAC foil tape over the seams of your plywood. This is cheaper than buying caulk and caulking every seam because you can buy a 100’ role of tape for 10$. Typically, house sheathing will be installed with a 1/8 gap in between for expansion and contraction. That 1/8-inch gap can leak cool air. So, by using the weather tight HVAC tape you are creating a more air tight building, saving you money and creating an energy efficient home. now after you install your sheathing you have a multiple choices of house wrap. Matt Rissinger an expert builder in Texas has done a study showing how much better Tyvek house wrap is compared to house brand home wraps. The Test he does might surprise you. So just by choosing a more quality house wrap will make your home addition last that much longer. As you can see, when you’re on a budget and need to make your home more energy efficient, it really can come down to the little details. Making sure your using adequate sealant where the skeleton meets the foundation, choosing a good sheathing material, and equally as important purchasing a quality house wrap.
Switching gears from wall framing and house wraps, it’s crucial for houses to have an umbrella. When I say umbrella, I mean the roofing over hangs should extend past your house more than 12’’. If you look at older homes that are still in great shape today, they have large over hangs that protect rain from getting close to the house. If you think about it, when it’s raining outside and you have a large umbrella water doesn’t even come close to you, when you carry a smaller umbrella, the water doesn’t directly hit you but when the water rolls off the umbrella and hits the ground, the water than splashes onto your feet and legs. By having a large roof overhang, it protects your house that much more form rain damage and decay. When we talk about roofs we have to talk about proper flashing.
Installing flashing and putting that extra bead of caulk could save you big money down the road if there is a leak. We are talking about pennies on the dollar here, caulk, flashing metal, roofing nails. A lot of home owners or DIYers will install T1-11 right to the sheathing of their homes without even installing flashing. It’s crucial to install some form of Z flashing at the bottom of the house where the siding ends. By installing Z-flashing and having the bottom of your house wrap end on it can save you large amounts of money and time. T1-11 isn’t a 5-star product but it gets the job done. When water does penetrate T1-11 and hits the WRB (weather resistant barrier) you want to make sure that when the water drips down the WRB it doesn’t hit any of your framing members. By installing Z flashing, the water dripping down the WRB will drop right off the house and into the ground, protecting your house from water damage and decay. Just a simple way of making your house more energy efficient and all around a quality build.
In conclusion, whether you have some money to spend to ensure your dream home addition is built right or just a couple extra bucks to throw at it, it’s important to look at every little detail of your home addition. In mesa Arizona, we won’t have rain at all and then all of a sudden it will rain 3” in just 3 hours. It’s crucial you look at every step of the ay from the skeleton all the way to the finished product. Just a simple bead of caulk in certain places, buying some extra flashing, breaking that thermal bridge with poly Iso, installing larger roof over hangs, or just putting on a quality WRB will save you money in the long run. I hope you guys enjoyed this blog and make sure you guys check out our social media pages and give us a follow!