Efficient Home Walls: A Good Construction Manager Knows These Rules
If your building or renovating a home in the Bay Area and are installing walls in your home, you might think “can’t be that hard to do right?” You’ve seen it in the movies or on TV, maybe even in real life. You nail in some studs, put up some drywall and you’re done. Right? What can be so hard about a vertical structure that supports weight and keeps out the rain? I hate to burst your bubble if you wanted to try DIY home walls, but there is much for a Construction Manager to consider if you want walls that will last and prevent things like leakage and mold.
A good construction project manager will make sure your walls are fit in perfectly. But if you are attempting this home project on your own here are some things you will need to consider:
- Leaks: Think about how many building have you been in that have had leaks around windows etc. I can’t tell you how many times I have seen wall building mistakes made in high end homes. As the project wraps up in the summer everything looks perfect, but a few months go by and the homeowners get their first rain. The best case scenario if a mistake was made is that the home owner actually sees the leakage, worst case: they don’t see it until several months go by and mold starts to form around the windowsill.
- Mold: Oh right, with leaks comes mold. How nice to see that black fuzzy growth at the corner or the room. Not only is it unsightly but it can cause some health issues. You may find yourself wondering why you have a residual cough that won’t go away.
- Cold: How often do you find yourself moving away from the window or exterior wall because it’s cold. It can also be slightly embarrassing when you notice your dinner guests are sitting at the dining room table still wearing their coats.
- Air leaking in: Maybe you do manage to heat your home but you wonder why your electric bill skyrockets so much in the winter.
A well built, modern wall solves all the above problems, but it is tricky to design and build the walls while making sure all the parts work together well. What you, as the homeowner, are looking for is a way of combining commonly available materials to create an inexpensive assembly that supports weight and provides comfort, while at the same time avoiding any of the problems mentioned above.
In this blog I will borrow images and concepts form an excellent lecture given by John Straube, Principal, RDH Building Science, Waterloo, Canada. I heard him give this lecture in the North Bay a few months ago.
An ideal wall has the following components:
- Thermal Control
- Water Control (Prevent water from entering)
- Air control
- Vapor control: Allows the wall to breathe
- Ventilation and drainage space behind the exterior siding to allow it to dry.
- And of course structural support.
Simple you say: We have done this for decades in areas that have wet and dry seasons like Napa, Sonoma, Oakland and Marin; wood studs with insulation between, some product to cover outside and inside, a window or two and done
Well, here’s the deficiencies that have become apparent over time:
- Thermal transfer: The wood studs are responsible for transferring lots of heat out or cold in. Yes, the insulation in between the studs helps, but there are some limitations. The studs themselves are responsible for quite a bit of transfer. More on insulation later in this series, but it is important that it be installed correctly.
- The current concept is to do what is called continuous Insulation, or CI. More on this later.
- Water intrusion, (leaks): The products available for this purpose have improved greatly from tar paper to modern compost materials that work like gore-tex does in your clothes and boots. It allows water vapor to pass through but does not allow water droplets to enter.
- Air leakage: We need to build houses and buildings that are comfortable without using tons of energy to maintain warmth or cold. We have found that air movements accounts for a large part of heat loss, or gain. There are many products to control this and sometimes this is the same for the water barrier. The current term is weather barrier.
- Ventilation space. We have learned that exterior siding materials, be they wood shingles, wood boards, plywood, or cementitious material (best) lasts much longer if there is a gap behind it that allows water to flow down and air to circulate. This can be achieved with furring strips or with mesh material such as Benjamin Obdike Slikker.
- As for structural support, the less wood the better from a performance basis. The use of 2 feet on center framing where joist and rafters are stacked above the studs is gaining favor as advantageous in that it uses less wood and has less thermal transfer.
In an upcoming blog we will elaborate a little bit more on the products and methods to achieve an efficient and comfortable and durable home.