Review of Boxabl SIPS Prefab House
The company Boxabl has created a metal SIPs (structurally integrated panel) house that has caught a lot of folks’ attention.
The main reason it has gone so viral is that it promises it all – fast, easy, cheap, resilient, and healthy.
My job as a Building Biologist is to review homes for durability, indoor air quality and resilience to mold.
It may be cheap and fast, but is this home a durable and healthy home?
First, is it “eco-friendy”
The basic structure of this house is a steel and styrofoam structural panel. This is very safe even for those with chemical sensitivities. That part has practically no offgassing and I am a big fan of SIPS.
They also use MgO (magnesium oxide) board on the interior surfaces which is generally safe option as it has extremely low or no offgassing in my experience.
It’s not clear how that is attached to the walls in this case, it’s likely glued on, which could be a problem for offgassing. (More on in the inherent risks of MgO against steel below).
The flooring appears to be glue down vinyl, though they have described it in different ways. The countertops and tabletop are laminate (which is a melamine plastic glued onto a substrate which is almost always MDF). And the interior cabinetry is conventional (which is typically particle board and laminate).
These three elements will contribute to offgassing – VOCs, plasticizers and glue from the vinyl floor; glues and formaldehyde from particle board based cabinets; and glues and formaldehyde from MDF based laminate countertops.
While this is not high in offgassing per se, according to conventional wisdom, it absolutely could be too high for those who are sensitive to formaldehyde.
At this time the interior cannot be customized and it includes all the interior finishes other than the bed and sofa.
Even though it would be quite easy to choose your own healthy floor and cabinets in theory, it would likely be difficult to remove the already glued down vinyl.
With just a little more effort this company, they could have reduced offgassing significantly by choosing better cabinets, countertops and floors. (Though keep in mind we do not know the exact materials or brands used so I am making some best guesses based on what is most typical right now).
Is it a durable design?
In general, metal SIPS are very resistant to mold because as long as the wall remains laminated they are immune to condensation problems. Moisture cannot get into any wall cavity to find a cold spot to condensate.
If they are well connected and well sealed then they could also be durable against leaks. The waterproofing will depend on how well the seams are connected. I owned a metal SIPS trailer (Camplite) that was very leaky!
There are a number of concerns I have with this house:
- There is a clear negative lap at the bottom of the first piece. It’s not just an exterior trim detail, it’s integral to the design. I don’t see how you would not always be battling water pooling up and soaking the wall.
- It’s nice that it unpacks quickly into a full livable house but how are all those seams waterproofed? I do not think we have enough information on that right now.
- Because it’s done almost entirely in a factory we would need to see a detailed factory tour to see if this is a good design (the company does not yet have a full-sized factory and is still raising money at the time of writing). There are so many details I would want to see including how the windows and all seams are waterproofed.
- The house, like all prefabs, needs to be seen in person, especially during installation to see if there are any areas vulnerable to water. Because this company does not have a show house and is not in full production yet, it’s highly unlikely you will be able to see one any time soon. My prefab post goes over the due diligence needed here, and with this house, we don’t have enough information to even do the due diligence.
- MgO and steel have not gone well together in the past. In Denmark, massive problems (and lawsuits) resulted when salts naturally leached out of MgO board and corroded the metal in the buildings.
- The website says that Boxabl “doesn’t use lumber or sheetrock” and in an email they said “we do not use wood or materials that can rot or mold”. But in multiple videos, wood appears to be the framing of the edges of the SIPs. Hidden wood in a metal-based house is a problem in my books.
Is this a reliable company?
Still in development
Well, I don’t think we know if this is a reliable company yet. As I discuss in my general prefab post I never go with the prototype of a prefab. They commonly have problems.
There could be situations in which we know a lot about a company, the construction details, and the testing of the prototype, but I don’t see enough information here to be confident.
The company needs to raise 10 million dollars to be in full production, and at the time of writing they are still raising money. They are not yet at production stages.
On the fundraising page it says “early investors get a discount”. When someone asked what the discount is they responded “It is possible there will be a discount. We haven’t announced it yet.”
In one of the videos, the rep states that you could install this without a foundation or permit. That sounds ill-advised.
It does not seem like the reps actually know what the floors are made of.
Elon Musk Involvement
It definitely adds legitimacy that Elon Musk is living in one. But it’s unclear whether he is backing the company or not. His area of expertise is not in construction but it would be great if he did lend his mind to making this a better built home than what it looks like. It has great potential to solve the problem of lack of affordable and healthy housing around the world. But in my view this house has not proven itself yet.