What Is Green Building? A Home Builder Explains (A Home’s Structure)

The concept of “Green Building” (or energy-efficient building), has over the last decade become one of the most important elements of the home building process that we work with our clients on. The massive amount of information available on the internet has allowed for the average home buyer to become much more educated on the topic, but this “internet education” frequently has significant gaps, and sometimes even outright misinformation. I will be dedicating a series of blog posts to a general review of the most common and cost-effective energy efficient building techniques employed in the Front Range area of Colorado.

First, I’d like to identify what will and will not be addressed, since the term “Green Building” encompasses a massive amount of territory, and can mean different things to different folks. In this series, we will not be discussing the environmental impact or sustainability of resources, off-gassing of VOCs (volatile organic compounds) or other chemicals, or specific energy programs such as LEED®, Energy Star®, etc. Instead, what we will be looking at is specific building systems (stick frame, ICF, and SIP specifically), insulation systems, heating/cooling systems, and solar energy systems. Also, for brevity, I will only refer to heating (and not cooling) in our discussion, since in Colorado that is our predominant need and focus. Lastly, I will discuss ceilings and not roofs, again just for brevity.

When I engage in discussions regarding energy-efficient building techniques and systems with people, a majority of the time the conversation is geared towards answering two overarching questions: “what will the upfront cost be?” and “what is the estimated time to payback?” Therefore, these articles will be “fiscally minded” at their core; my clients have demonstrated to me that this is their predominant criteria when considering energy efficient systems. On a personal note, I do not “have a dog in the race,” so to speak; my goal is to help my clients arrive at their best decision and to execute on that decision. Over the years I’ve worked on a few projects that have minimal energy efficiencies, while on the other extreme I’ve worked on a LEED® Platinum project, and I’ve worked on LOTS of projects that are somewhere in the middle of those two extremes, and I was happy to offer my services to every one of those projects.

Moving forward, let’s dive into the concept of building systems – the structure by which the walls and roof of a home are constructed. For the past few centuries, wood has been the material of choice for builders. The material is cost-effective, the labor pool for installing it has been deep, and it installs quickly in virtually any weather – all good reasons for building a home out of wood. (In the construction industry, we call this method “stick framing”). Additionally, with wood, changes are easy to make, and subsequent trades (plumbing, electrical, HVAC, roofers, stucco/siding) find it easy and efficient to work with as well. So where has the stick framed dwelling fallen short when it comes to energy efficiency? Two specific areas: air infiltration, and thermal bridging. Air infiltration is the enemy of an insulated envelope, reducing the effectiveness of the insulation and heating systems. Air infiltration is a big issue with stick-framed homes, for two reasons.

First, the wood framing itself lends itself to being “leaky” – lots of air movement can occur between the interior of the home and the exterior of the home, as the wood members and the exterior sheeting allow for air to flow between the two. Add to that, for many decades batt insulation was installed in the bays of the walls and ceilings (bays are the open spaces between studs and joists/ rafters). Batt insulation is the least effective method of insulation we currently employ; it too has lots and lots of air infiltration, reducing its overall effectiveness.

Then we have the concept of thermal bridging, which simply means that the wood members of a wall or ceiling do not have the same insulation value as whatever insulation system is being employed, thereby reducing the overall of insulating value of the wall or ceiling system. Specifically, a 2×6 stud has an R-value of just under 7, so if we factor in that roughly 20% of a wall’s total area is comprised of lumber, you can see how much that reduces the total insulating value.

In recent years, two alternative systems to the stick framed home have emerged and established what appears to be a permanent spot in the residential building industry – SIP (structural insulated panels) and ICF (insulated concrete forms). We will take a look at these systems in our next post, along with addressing the question – “Is there hope for the stick framed home?” Spoiler alert – the answer is YES!! Thanks for reading, and stay tuned for the next post!