Our next Passive House scheduled to begin summer of 2018.
We hear the term “energy codes” in a myriad of ways these days. What do they all mean and what is the difference between the many prescriptive guidelines?
To begin with, all local Building Codes are required to provide some level of energy code in their local code structure. The most commonly integrated codes throughout the United States is the International Energy Conservation Code (IECC) originally issued in 2000 and revised in 2003. Thats not a typo; this code is over 15 yrs old and found all over the US today.
The image above shows all the residential energy code standards today. The green box to the right is where most jurisdictions fall today with a HERS rating of close to 100. LEED built homes are closer to 60 and the Passive House (PH) standard is near 0. These values are based on net energy use and do not take into factor renewables.
This is straightforward enough but further complicated by the varied climates found in the US. In other words, living in Montana requires a heating based energy demand while Florida residents will be geared towards cooling instead.
The above map shows the 7-8 climate zones and their respective locations in the United States. States like Colorado, Arizona and California have 3-5 climate zones each showing the vast difference in the local environment due to elevation, latitude and climate conditions. This translates into more than one energy code needed to be truly effective at dictating a standard.
This slide shows how the US dictates energy codes. As you can see, it varies state to state with the 6 white states having no statewide code meaning that local jurisdictions are responsible for implementing an energy code, or not.
One of these states, Colorado, is where I reside. As the map below shows, county by county climate zones vary widely. The graph of values to the right show recommended values for climate zone 4 and 5. These are recommendations only and are used as minimum values.
So what to make of all this information?
Understanding that energy codes, where found, are largely minimum standards that set the bar for R-value of walls, roofs, slabs and windows, we can draw the conclusion that these numbers are not directly associated with saving energy use but providing baseline standards for the public to follow. Then understanding that most entities building homes, whether developers or builders, have their eye on the bottom line of built-out costs, its no wonder we largely have inefficient buildings in the US today.
More stringent codes like the Passive House standard advertise a net energy savings of 70-90% over the standard codes. This is substantial when taken into account that over 40% of the energy produced in the US goes toward the conditioning ( heating and cooling) of buildings.
In Vancouver, BC and many areas of central Europe, building to a higher energy standard is encouraged by tax refunds, more flexible zoning and in some places, additional square feet of buildable area which can offset the added costs of high-performance efficiency. And in these areas, high-performance buildings are becoming the norm.
Here in the US, we have enjoyed years of relatively cheap energy and thus have not put much effort into building efficiency based on economics. As climate change and a warming climate become more accepted to discuss and combat, it sure seems that having tighter residential energy codes would go a long way towards making a difference.
How do we create a virtual air-tight assembly in a building?
The quick answer is tape and perseverance. Below the slab we install a 15 mil vapor barrier that is taped and flashed at all penetrations. This barrier will be the first step towards sealing the building as well as removing any risk of radon from the building. (more on this in a future post)
From here, this layer is attached to the exterior wall sheathing and then the sheathing is taped at every possible seam. Now we have a underfloor and wall system acting as one unit.
The bottom of the roof or ceiling plane then gets taped similar to the walls. All lighting penetrations, vents or access panels must be treated with detail to pull this off.
The windows and doors are then installed and air sealed with tape or wet flashing. Once this is complete, we conduct a blower door test to scientifically measure the actual air changes per hour or ACH. Our goal is .6 ACH.