What is different about Passive House construction?

Passive House construction is planned to be performance based.  That performance relies heavily on how much attention to detail there is during the construction phase.  One of the key principles of Passive House is that the project have a continuous airtight layer.  This is extremely important.  If you have built tight houses before, you may have been happy with an ACH of 5 or 6.  For Passive house that ACH needs to be .6 or BELOW.  That means you need to supervise the installation of all materials and connections to make sure they are installed properly, sealed properly, and connected to each other properly at the airtight layer.  You need to stress to your workers that if they happen to accidentally pierce, slice, cut, stab, rip, or make any other penetration through that layer it needs to be sealed back up with the proper sealing materials.

The materials that are used should be familiar, such as glues, wraps, foam, insulation, and weather seals, but it is making sure they are installed properly, that bays are insulated fully, that sealants fill all voids, that wraps are taped at all seams, and taped to the windows, that doors and thresholds are airtight.  The windows will be another key element.  These will be triple pane in most applications.  They will be designed to be a specific size.  The rough opening will be set to be a specific size too.

When it comes to the plan, you will need to understand that it can not be changed on a whim.  You can not decide to fill in a rough opening that is too big by layering 2×6 in the gap until it is filled – the r-value of the wall has been calculated based on the materials that are specified on the drawings.  Other materials or installations will need to be approved for their r-value if a change needs to occur.  This is because the house is designed to operate to a specific set of comfort principles.  That means that thermal bridges are extrememly reduced or eliminated so that the residents will enjoy a steady 68deg environment.  If you change how a wall is designed, you introduce a change in the r-values which can result in heat loss and can also introduce other potential problems such as mold.

Prior to the project beginning, you and the key members of your crew should attend an information session given by the Certified Passive House Consultant who will go over the basics of Passive House, and layout what the critical areas and needs are for that project.  They will be able to answer any questions you have and go over the reasons for the specific materials that are called out.  During the project, if you are unsure of how a procedure fits with the Passive House concept, be sure to ask while there is time to keep the project moving forward.  It really is construction as you know it, with extra attention paid to the details so that it should perform as calculated.