Temperature, climate, & energy management for 1984 Airstream renovation
Hi all,
My partner and I recently acquired a 1984 Airstream Sovereign (180 interior square feet) which we are gutting and remodeling in tiny house fashion. We’ve been dreaming about going tiny for a while and living smaller, more sustainable, less wasteful lives, and now it’s time to make the dream happen!
I’ve been doing lots of research on my three topics noted in the title: temperature, climate, and energy management. I would love some advice! We want to do this job right, which means doing it green.
Like I said, we are gutting the trailer so we have an opportunity to put in entirely new systems, so I want to be careful with our decisions. We have found THREE independent heating systems that were installed at various points–one propane, and TWO different electrical systems. We obviously want to streamline this.
So, in brief, my two big questions are:
1. Insulation. A friend of mine converted a Sprinter into a full time home and used Havelock wool for insulation. From my reading, wool seams like a great fit. Higher insulation levels (R-values of 7+), sustainable and healthy (i.e. not toxic like most insulation), sound dampening, moisture regulating, etc. Would members of this message board also recommend wool? I know it’s more expensive, but again, doing it right and doing it green is my goal.
2. Climate. I have very little knowledge here so this is where I need a lot of help. AC, HRV, heat: is there one system that would do all of these, or a combination of systems that has been shown to work well in an aluminum can like ours? From what I’ve read, an HRV like the short version of the LUNOS e2 sounds effective, but there are other HRVs that also look good (and cost less). Would this replace an AC system, or work in tandem with it? And then what sort of heating system would be the most efficient to install with these? Trying to find a balance of effectiveness and energy usage.
I ask all of these questions because we live in the Pacific Northwest, currently in a basement suite with a lot of concrete and tile and no control over our own heating other than an aftermarket dehumidifier unit. Without it, we have crazy moisture levels and I want to avoid this in the Airstream. As it stands, we have a LOT of mold to deal with from a poorly regulated space, and I don’t want to clean everything only to have it get moldy again.
In the summer, we will likely have windows open for natural air flow most of the time, but as we are planning to be finished the reno by February, a very cold and damp month in our area, I want to make sure we taken all these considerations into account.
I’ve attached temperature and humidity charts for Vancouver, BC, where we live for all of your reference. Thank you for your patience with this large project and these very general questions!
-Eric
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Replies
The safe bet is to recreate the factory setup as this is a time tested system.
How much wall thickness are you willing to give up for better thermal performance?
Most of us are not familiar with air stream construction. I am sure it is a series of comprises wall thickness vs. strength vs. weight vs., thermal performance vs. fire safety.
If your trailer has a metal frame that connects the interior to the exterior surfaces of the walls this will make effective insulation very difficult as the metal will conduct the heat thru your insulation. The cold metal on the interior is very likely to fall below the dew point inside the trailer so it will get wet and likely grow mold.
You may want to Google “fema katrina trailers” and learn from those mistakes.
Walta
Hi Walter,
Thanks for the response! We are, in fact, recreating the factory setup, but with some modern innovations used in new Airstream construction, and in tiny houses with similar square footage.
The construction is an aluminum shell + 3ish-inch aluminum ribs + an interior aluminum skin with a laminated wallpaper-like surface on the inside. Thermal briding is definitely a concern, then, especially since through the winter we consistently hover around a very damp, chill freezing, and typically get down to -10C/14F temperatures in mid-winter. People have used polystyrene tape on the inside of the ribs which seems to help, and combined with a good insulation heat loss can be mitigated... hopefully!
The question remains on climate control apart from insulation, though. If we assume we've insulated it properly, given the construction I've described here, are we looking to install an HRV for winter and AC for summer, and just make sure to flip them when we hit the appropriate temperatures/humidities season to season?
My partner and I have been doing more research, and a lot of vanlifers install these Dometic Fan-tastic Vents (https://www.dometic.com/en-us/us/products/climate/ventilation-solutions/rv-roof-vents), and we're considering them because they'd be a lot cheaper than a LUNOS system, and they would fit our exisiting fan/vent cutouts in the roof. It seems that two of these could be set up to suck in fresh air and exhaust stale air, but they don't appear to have the heat recovery feature of an HRV.
Can anyone with experience with such a small space weigh in?
Thanks,
Eric
I’d be reluctant to use wool, or any non-treated natural fiber insulation for fear of critters nesting in it (I’ve has problems with this in the past). Also, aren’t airstream trailers the really rounded ones? That’s going to make things tricky, and probably rules out any rigid insulation. Dense pack cellulose comes to mind.
For the ribs, thermal bridging is going to be a real concern. Aluminum is an EXCELLENT conductor of heat and many things INTENDED to conduct heat are made from it. Aluminum is a way better conductor of heat than the steel most are used to dealing with in construction. Anything you can do to create a thermal break will help, even little strips of the 1/4” Fanfold XPS insulation. Can you provide some pics of the rib assembly so that people here can give you some ideas?
For heating and cooling, I think a small (very small :-) minisplit would be perfect for you here. These little systems can do heating AND cooling, and can do both pretty efficiently.
Are you doing anything creative for power, or are you planning to just go the usual “plug in at the park or run a generator” route?
Bill
Hi Bill,
Yes, with wool, that is the big concern. On every other point wool sounds like a better option: air quality, moisture control, mold suppression, sound absorption, fire retardance, and sustainability/renewability/non-toxicity (https://havelockwool.com/fiberglass-insulation-vs-wool-insulation/). A little context: I work in the outdoor recreation industry, where NZ wool is THE super material for climates like mine, so it made intuitive sense to me that it would make for good insulation. But I'm no professional, so I value all of your opinions!
But back to main point: critters! Havelock treats their wool with "a minor amount of boric acid ... as an insect repellent" (https://havelockwool.com/van-insulation-products/). So it is treated, at least to some degree... But again, no professional here! I'm more concerned about insulation toxicity and air contaminants in such a small space, and this wool seems like a really good solution.
The Fanfold XPS like it would be a good option for the ribs too! We don't have the skins off inside, but this blog (https://amontereyblair.com/interior-skins/) has some great photos for reference. The third picture down shows the inside with the skins off, and you can see the ribs all the way along. This blog (http://beahmstream.com/insulating-an-airstream-part-2-practical-application/) also has some great info on a rather eccentric insulating process, which is where I got the polystyrene idea from.
For power, we are going to be running off of "shore power" most of the time, as we are not planning on living on the road full time. We are, however, looking at installing solar as a supplementary system. An electrician friend of mine is looking at options for us, and he's the one who told me to start digging into insulation and climate control because that would be a large determiner in our energy needs! If we just lose heat constantly, or can't keep the space cool in summer, then we're obviously going to waste a ton of energy trying to regulate the climate in the space!
Hope the extra info helps!
Thanks,
Eric
I’d be careful getting too much info from a trade association style website that exists to promote any particular product. Every product has pros and cons, but marketing people will play up the pros and downplay any cons which isn’t the best way to educate yourself. The nice thing about sites like GBA is that for the most part, no one cares about selling anything so you tend to get better info as to the actual usefulness of any particular product in your own specific application.
For me, I don’t buy the “better air quality”, but I’m biased against wool because I’m allergic to it :-) I’m not a big fan of denim insulation either, mainly because it’s heavy (which can be a plus for sound control sometimes). I would probably try to use blown cellulose in those wall cavities you have.
In terms of air quality, any insulation inside those walls is going to be pretty well sealed up. Cellulose’s big downside is it’s dusty while installing it, but once done, it pretty much just sits there. It’s very good for filling cavities where you can just pour the stuff in with the blower. Batts are more work, since you have to fit them neatly into cavities for best performance, and you need full access to the entire cavity and not just a hole.
There is no question you’ll get the best overall performance from rigid foam if you can make it work. The big downside to rigid foam is that IT’S RIGID! (Duh :-). It will be difficult to fit rigid foam onto any surface that isn’t particularly flat. If you’re worried about offgassing, both EPS and polyiso have pretty much no issue with this, especially in the case of EPS.
I’d try using reclaimed polyiso here if you can make it work. 1” polyiso will give you about R6, and it’s cheap too. Using any reclaimed insulation is more green than using any new material since you’re basically recycling the product and giving it a new life — nothing new had to be manufactured! You also save money, so it’s a win-win. You could still fill the cavities with something like cellulose if you want to help with sound, or to gain a little more thermal performance.
Bill
Just doing a rough calc with 3" AL ribs, I think you end up with something like an R3 wall if you insulate with R11 batts. Pretty much, there is no point in bothering with the walls. If it makes you feel better, you can drill a couple of holes and blow some insulation into the walls.
I think it would be easier to leave the existing interior skin and install a layer of of rigid insulation on the inside. You can go with 2 or 3 layers of 1/2 polyiso, you can score one side a bit and bend it around the curves. This would give you between an R7 or R10 wall depending on the thickness. You can also cut grooves in the polyiso to run your wires.
HRV and AC or two different things.
HRV/ERV is for venillation, this should be running all the time. In a small space, the air gets quickly used up with a couple of people, you need something to bring in fresh air all the time, you never turn it off. Simplest is one of the WhisperComfort ERV bathroom fans. There is a ducting kit for it so you can run the fresh air supply to the living space.
Heating and cooling, easiest is either a through the wall PTAC heat pump or a mini split. Mini splits are quieter and more efficient but cost about 2x to 3x to install. There are also PTAC specifically designed for mobile homes that can be installed through the roof.