Plant Prefab Goes Passive House

Steve Glenn founded LivingHomes in 2004 as "a designer and developer of modern, prefabricated homes that combine world-class architecture with an unparalleled commitment to healthy and sustainable construction." I met him that year at a modern prefab conference in Austin, Texas, when I was working with a prefab company in Canada, trying to make it easy for people to get great designs by some of the best architects, and trying to convince architects about the benefits of selling plans as part of a catalog.

I could never convince people to pay more than the going prefab price per square foot and filled my days blogging about prefab, which is how I ended up at Treehugger. Steve Glenn persevered, hiring the likes of Ray Kappe and Kieran Timberlake to design houses for LivingHomes and then Plant Prefab, a prefabricated design and construction company in California. And now, many years later, architects understand the concept.

One of those architects is Richard Pedranti, who I met in 2016 at a North American Passive House Network conference in New York City. He has been working with the tough Passive House standard and various forms of prefabrication for years on the east coast. He has now partnered with Plant Prefab to launch the first Passive House LivingHomes, introduced with three designs – called the RPA LivingHomes – ranging in size from 2,218 to 3,182 square feet. I wondered how Richard on the east coast got tied up with Steve on the west coast, and was told:

"Richard had actually reached out directly to Steve about collaborating since he had been following the work that Plant has been doing over the past many years. Steve let us know that that is more and more how collaborations are coming together – architects are eager to work with Plant, and are getting in touch."

This is great news, what I was trying to do so long ago. It's good for architects and good for clients, who get to chose from well-resolved plans by talented architects. They know what they are getting and how much it is going to cost. This was always the promise of prefab.

Party Like It's 1799 In Your RPA LivingHome 2

Two of the three houses have a simple, classic form with steeply sloping roofs; there is a reason that houses have had this shape since Colonial times – it's a really efficient use of materials. Every time there is a jog or bump in a building form it results in more surface area and heat loss, so Passive House designs like to be simple, or as architect Bronwyn Barry describes them on Twitter: #BBB or Boxy But Beautiful.

There is a reason they are relatively large as well; prefab gets more cost-efficient as it gets larger because setup and fixed costs are the same, as is the expensive stuff like kitchens and bathrooms inside. A big boxy Colonial house form is the most cost-efficient house you can build, and that sloping "forever roof" will shed snow and rain and is great for mounting solar panels at just the right angle. I have called Passive Houses "dumb homes" because they don't need smart stuff to be efficient, they do it with basic things like insulation, high-quality windows, and airtightness. Architect Mike Eliason calls the form "dumb boxes" noting that they "are the least expensive, the least carbon-intensive, the most resilient, and have some of the lowest operational costs compared to a more varied and intensive massing."

That's why when I was trying to sell tiny modern prefabs, the only thing my clients ever wanted was a three-bedroom two-bath boxy colonial at half the price per square foot.

A few years ago I had this discussion with Tedd Benson of Unity Homes, who was offering a modern version of the Colonial Dumb Box called the Värn, and John Habraken, one of the most important thinkers about building design, concurred: simple boxes with forever roofs make sense.

One complaint that people have about Passive House is that the windows often seem small, especially if they are not facing south; the solar gain has to be carefully calculated and the heat loss minimized. So here you see a couple of things going on: there is a big overhang shading the ground floor, carefully calculated to let the winter sun in and keep the summer sun out. I like how the garage is separate too; it keeps any exhaust separate and simplifies the building envelope calculations.

The plan is absolutely classic too, this has been done since bathrooms were invented. Note also something you rarely see anymore: bedrooms with windows on two walls, perfect for cross-ventilation. It is just what you need. I have written before, in Lessons from Grandma on Green Building and House Design, about how our houses have changed:

"We've eaten up much of the energy savings by having house size get out of control. We've complicated our designs as if we wanted to maximize jogs and surface areas. We've introduced double-height spaces and media rooms and family rooms and breakfast rooms and ensuite bathrooms for every bedroom. We have forgotten about orientation and cross-ventilation because we can just turn on the air conditioning. We get rid of asbestos and lead in paint but don't question brominated flame retardants and phthalates."

These houses remember all that stuff. The ground floor plan is shockingly retro, right down to the giant utility room at the side entrance. The only thing I believe it gets wrong is the location of the 2-piece bathroom (powder room); as I described it in an earlier post on Home Design Lessons from the Coronavirus, it should be in that big utility room because everyone comes in the side door. I learned from my boss:

"Years ago when I worked in the prefab modular home biz, I asked why the powder room was often placed in what I thought was a weird place. Pieter, the company owner, told me that most of the homes were built on lots in the country for working people who drive long distances and they often want to dump their work clothes in the laundry room and wash up. So almost every house had this arrangement, where you entered the home essentially through the powder room and laundry."

The buyers of this home probably won't be farmers, but they will still be mostly coming through the side door, so it makes sense to put the washroom there. But other than that, I have to note that in my years selling prefabs I would push the fancy architect's designs that I had commissioned and nine times out of 10 would end up selling this plan, which has the program and plan most people want in the most cost-efficient form. The fact that it is the most energy and material efficient form you can build is a very nice bonus.

RPA LivingHome 1

The LivingHome 1 takes a similar approach in what is essentially a single-floor plan with a loft for the kids built under that big roof.

I find this plan to be problematic. It tries to keep it simple, but what is called the entry hall (1) is at the side porch, the main porch (10) and I guess the front door just dumps you into the living room, Hall (1) is miles from Bathroom (5) and the laundry, all those things I loved about the LivingHome 2 are kind of missing here. And don't get me started about the main bath having a combined tub/shower.

But the nice thing about prefabrication is that every iteration is better than the one before, there is continuous improvement and refinement. An architect as good as Richard Pedranti will figure it out.

I am not going to touch LivingHome 3, I could spend a week discussing its plan. I get the sense that Richard Pedranti is trying to go Californian and that it needs a lot more work. It's also huge. You can see it here.

I will instead go back to what I love about this program: the fact that Steve Glenn and Plant Prefab are making it possible for other architects to be part of its collection. I learned at a personal cost that what I as an architect think people want, and what customers who have been looking at and living in all their lives actually want, can be two very different things. So it is good for everyone to have as many options as possible.

The other great thing about the RPA LivingHome designs is that they are going for full Passive House certification. This requires a certain rigor in design; you can't fake it. We have shown many homes designed to "Passive House principles" but that are not certified, probably because the architect or client wanted some design feature that caused it to miss the standard. But as Bronwyn Barry notes:

"Today we see more and more buildings claiming to be Passive House buildings or they are advertised as 'being built using Passive House principles' – be skeptical. We see these buildings that are alleging to be Passive House buildings, falling short of owner expectations. So buyer beware. If the building is not certified, is not certified by one of these certifiers, your risk of not meeting your targets, your risk of producing a gap in performance, can go up significantly."

Instead, this is the real thing: Good designs from talented architects, with high-quality construction from a sophisticated builder, to the highest standards of efficiency, comfort, and health. That again is the promise of prefab.