Adventures in Passive Solar Heat Mitigation

The building Lab B occupies at 12-22 North Street was built in 1979/80 as a state-of-the-art passive solar demonstration project. With R-40+ wall insulation, a large brick thermal mass bisecting the building, and large arrays of south-facing windows on both the first and second floors, 12-22 gets and stays toasty in the winter.

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The seasonal logic of overhangs in passive solar design.

While the front overhang helps a bit, it also gets toasty in the summer-time (particularly the southern offices), and we discovered just how toasty when the A/C unit died in the middle of July with no prospect of replacement until September. So, some hardcore kludging was in order…

To start, we immediately aimed to deploy a few portable air conditioners, but ran into to the fact that virtually all the windows are casement windows. So, the only kind of A/C that could work would be a portable one with a hose rather than a window unit, and we needed to figure out how to get the hose out with the remainder of the window sealed.

The best solution I found was a cloth adapter that attaches to either side of the window via adhesive velcro strips. In the center is a zipper with two pulls, so the exhaust tube can be zipped in and form a decent (but obviously not perfect) seal. One obvious downside is that it does not provide security, so for the window facing the street (rather than behind a fence) I ended up taking it down and closing the window at the end of each day. With the velcro, that was not a huge pain – once you have the hang of it, it’s maybe a minute to deploy, and less to break down.

I this is the hottest summer of my life GISTEMP Annual Trend 1979-2019 this is the coldest summer of the rest of your life - America's best pics and videosThe portable A/Cs took some of the edge off, but were clearly insufficient to get and keep the building at a comfortable temperature, particularly with “Earth’s Hottest Summer on Record” heat waves rolling in. So, in addition to our machines desperately pumping heat out of the building, we needed to figure out ways to minimize the heat coming into the building (“solar gain”).

The windows were already equipped with off-white cellular blinds which insulate and reflect a bit of heat, so my first addition was mounting some reflective bubble foil insulation to the interior of some windows, starting with the skylights. Being in a hurry, I simply used some loops of painters tape to adhere them to the skylights and some windows.

This approach made a dent, but had two signficant flaws. First, no matter how reflective the material, once light passes into the building, a significant portion of the energy of the incoming light is captured as heat inside the building envelope. And said heat concentrated between the foil insulation and the window. With sufficient exposure to those high temperatures, the adhesive in the tape weakened and my sun-blocks gracefully fluttered to the floor within a matter of days.

A far superior approach is to intercept the solar heat before it enters the building envelope. The most common way of achieving this is with reflective film that is applied to the exterior of the window. However, as we didn’t want to give up the helpful solar gain in the Winter to mitigate our Summer suffering, we needed a more temporary solution that could be deployed when needed, and easily broken down and stored when not. One of the nicer options seems to be solar screens, but they were beyond both our current budget and time-frame – we required something that could arrive and be deployed quickly on a budget.

Aluminet deployedAluminet interiorSo, the first thing I decided to try was Aluminet. It’s a reflective woven material that comes in tarps, and is commonly used for shading crops in hot climates. You can order tarps that let various percentages of light through. I ordered two tarps that block 70% and let 30% through with different dimensions, and mounted them over some of the front windows. They seemed to be fairly effective, while still letting enough light through that the interior space didn’t feel gloomy. Another benefit that became apparent when I mounted a reflective solid tarp over another window to perform a similar function is aluminet’s relative resilience to high winds. When a thunder storm rolled through, the solid tarp became a kite that I had to go running after, while the holes in the aluminet meant the wind passed through and blowing away was never a problem.

Suction cup exterior shadesA second affordable/DIY exterior mounted solution I came across found me reusing the sheets of bubble foil insulation that had fallen from the skylights earlier. The core idea is simple: add suction cups to the corners and stick them on the window exterior. After ordering a professionally manufactured version with a few week lead-time for under $20, I scrounged up some used suction cups to make a few (less attractive) DIY versions for immediate deployment. I only made them about half of the height of the window, as the top portion tends the be shaded by the overhang, and so they would block most of the heat while still allowing natural light into the offices.

As they accumulated, the exterior interventions made a meaningful dent on the solar gain, and gave our long-suffering portable A/C units the breathing room they needed to keep the building mostly comfortable.

With the arrival of the 45 degree nights of Vermont’s Fall, the urgency of this work has begun to fade, and installation of the building’s new heat pump has begun, so the end of the crisis period is in sight. However, the motivation of avoiding an 80+ degree office ended up teaching me a lot about the dynamics of solar gain. It also provided ideas for annual interventions (such as obtaining a full complement of the professional suction cup-mounted window coverings) that will, complementing the new HVAC, allow the building to operate far more efficiently in the coming (ever hotter) Summers.

Stay Cool!

Weekly Public Hours Every Thursday Evening!

screenshot of an image on wikipedia of a few guys standing around a table with ice cream on it with the caption 'people eating ice cream at a lan party'

We realized we hadn’t updated the site to note that open hours have resumed!  Come hang out with us every Thursday from 7pm-9pm (and probably later) at our space at 12 North st. (up the stairs at the side of the building.

Folks will be there working on personal projects, fixing things, chatting, eating, playing games and just hanging out. Come through!!

February 2023 Activities Update

We set up a Mastodon account. Toot @ us here.

Regular Activities:
  • Public Hours happening every Thursday from 7pm – (at least) 9pm in the space.
  • Repair Cafe 3rd Saturday of the Month from 11am-3pm. Volunteers and broken things welcome!
  • Monthly Member Meeting 2nd Saturday of the Month at 7pm, sometimes a potluck starting at 6pm. Drop a line about attending if you are interested in learning about joining the Lab.
  • Our most frequently active public online space is our Discord Server.
Possible Additional Activities for the Spring
  • Revival of the bike glow-up and ride (late April)
  • Some folks are talking about a monthly textile night

New Mask and COVID-19 Safety Requirements – December 2021

The Laboratory B membership has voted on December 12th, 2021 to introduce the following new policies in the interest of COVID-19 safety:

  • Anyone attending a public event in-person will be required to wear a properly-fitting respirator rated to at least KN95 filtration without exhalation valves. N95, P100, and PAPR respirators are also acceptable.
  • KN95 respirators will be available at no charge at any public event
  • Open Hours will be held virtually on Discord until further notice

We appreciate your cooperation in helping keep our community safe and healthy.

Old North End Repair Cafe – 20 Nov 2021

May be an image of text that says 'Repair Café Toss it? No way!'

Thanks to everyone who came out to the dance party on Friday night and helped raise a bit of $$ for the Repair Cafe! It was a blast, and we’ll likely do another one at some point.

If you want to swing by while we’re fixing things rather than flailing about wildly with glow-sticks, swing by the next Repair Cafe on Saturday, Nov 20!

Free and or Open Source Game Night

Join Lab B every Thursday night at 7pm for FOSS (free + open source software) (or sometimes closed source but free) game nights. Meet up on our discord and we’ll go from there. If we’re planning on a specific game it will be listed on our events page


EDIT: regular (weekly, unstructured, in-person) open hours have resumed!

Third Old North End Repair Cafe this Saturday August 15th!

The next Old North End Repair Cafe is this Saturday, August 15th from 11am-3pm. Come on down and volunteers will do our best to repair anything you can carry in! And if you’d like to help out, please fill out our volunteer interest form (free snacks for volunteers!). This is an outdoor, socially distant event and masks are required.

Also, going on concurrently will be Degrowth Fest which Repair Cafe will be a part of. We’ll have a poster illustrating the merits of repair 🙂

More info on our Repair Cafe page.


Second Old North End Repair Cafe this Saturday!

Hello everyone, here are the results for our first Repair Cafe last month. 70% success rate is pretty good! Especially for our first repair cafe. It looks like 29% bicycle but that’s actually sewing!

The next Old North End Repair Cafe is coming up THIS SATURDAY, July 18th! Come on down to 12-22 North st between 11am and 3pm (we can only accept new repairs until 2:15pm)

More info on our Repair Cafe page