Last week we took our first look at a Passive House going up in Arlington (which is Northern Virginia's first Passive House, just behind this one in Bethesda and another in DC). We're back this week with a more in-depth interview with the two brothers developing this project, Eric and Roger Lin. The two have been real estate developers for a while, but this is their first foray into Passive House design. Here they talk about the hows and whys of bringing a new technology to a country that hasn't had much experience with this type of building style. But they are both quick to point out they are not reinventing the wheel completely. Their gravel foundation is something that Frank Lloyd Wright advocated for during his career.
How did you decide on the Passive House system?
We looked into LEED also. They call that prescriptive because you get points for where your lumber comes from, what kind of materials you use. But it is possible to build a LEED building but have it perform poorly in terms of energy efficiency. For example, LEED might say you should use cellulose for your insulation because it is greener, but Passive House doesn’t care what you use. You can use fiberglass products if it creates the right level of insulation. What that allows for is different levels of entry for builders and developers. If you specialize in low-income housing you can build very cheaply with materials purely based on energy performance and still build to Passive House Standards.
What is the most expensive material that is specific to a Passive House?
Windows and doors. They just aren’t available in the US. It’s funny, the windows in the US are designed assuming they will leak and European windows are not. They are just not that available in this country—at least not from the companies most people have heard of like Pella and Anderson. Part of the problem is the style. In a lot of houses you see double hung windows, but they have too many “thermal bridges” (For windows it is actually more about potential points of air leakages) for a Passive House. Some Passive House builders actually see windows as a part of their HVAC system because that is where there are so many leaks.
How is your HVAC system different from the Passive House in Bethesda?
Our heating and cooling system is just a mini-split system. It is very small and pretty common in Europe and Asia for heating individual rooms. But with a Passive House you only need one for the whole house. It uses the equivalent amount of energy as about two hairdryers. But because it is a point source—meaning it is only in one place of the house—we have to use transfer fans to diffuse the air more quickly. In a standard house the air goes through a long duct system losing much heat along the way, but with our model the air on the first floor is drawn up through a diffuser in the floorboards, essentially shortening the duct to about one foot long.
The Bethesda house has something called an ERV. What is that and will your house have one too?
We use an Energy Recovery Ventilator also—they’re like the lungs of the house that filter the air as it comes in. In most houses you’re breathing through your skin (if you keep the analogy of the human body). An ERV allows you to get fresh air and expel stale air all the time but the energy is transferred between the incoming and outgoing air. That way you maintain the internal temperature of the house.
· Arlington Passive House by Southern Exposure Homes [Official Site]
· Arlington Gets In On Passive House Trend, Part One [CDC]
· Empowerhouse [Official Site]
· Bethesda's Passive House Construction Complete, Ready For Visitors [CDC]
· How To Build A House With Only Two Dozen Holes [CDC]
· The First Local Passive House Is Almost Finished [CDC]