Appropriate use of airlock
tupchurch
| Posted in Green Building Techniques on
I read Mr. Martin saying that, at least in a residential context, an unheated mudroom acting as an airlock does not save energy. What studies can I read about this? Are they nonetheless appropriate for a church or commercial space?
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Replies
Tupchurch,
You quoted me as saying, "at least in a residential context, an unheated mudroom acting as an airlock does not save energy." In fact, I wrote that the investment in materials to create an unheated mudroom will not achieve enough energy savings to be a cost-effective investment.
For a church or a commercial space, there are lots of reasons you might want a foyer: it's somewhere for people to gather, for example, and allow their clothes to drip during a rainstorm before proceeding to their business. In a church, that's where you put the holy water, brochures, and posters announcing church events.
I greatly enjoy reading your blog, sir. It touches on issues I don't find often discussed and you encourage a healthy skepticism of ideas many would like to keep as pets. I particularly find your comments on green lifestyle removes a lot of blarney from the conversation.
As for airlocks, I mean particularly the 6' or so space between sets of doors that I commonly see at commercial spaces like Walmart, Lowes, etc and also at large churches. Sometimes they store shopping carts there, but not much else. It's a transitional space, I take it, intended to reduce the amount of outdoor air from getting inside? Forgive me if it's an obvious question, but is this a comfort issue rather than energy or is it both on that scale of traffic? Curious, ignorant minds wish to know more than they do.
Hi tupchurch,
even if it does not save energy as an airlock, you can argue that a house with an unheated mudroom is more affordable compared to a house with a heated mudroom (house of same "net" size) AND will save energy because of the smaller envelope. A Mudroom like a covered porch - why not.
wastl,
"A Mudroom like a covered porch - why not."
Without some heat nothing in the mudroom dries, and the things you leave there are often uncomfortably cold to put on.
Can confirm, Malcom.
My house has an unheated mudroom, added on some time in the 60s (rest of the house is 1880, just outside Bozeman, MT, CZ6). It was built right on a slab that extends past the bottom plate of the walls to a walkway outside (yes, it is exactly as stupid as it sounds). Hot in the summer, freezing in the winter, floor slab is always slightly damp. I crank an electric baseboard heater in there all winter to dry out ski gear etc (which adds noticeably to the power bill), and without heat the space is pretty useless.
And Tupchurch, to your original question:
If I keep the mudroom unheated during the winter, it's still pretty uncomfortably cold near the interior back door that leads to the mudroom. I'm sure it creates some temperature buffer, but it's not much.
Not just cold--my mudroom is in the uninsulated, unconditioned ell of an old Maine farmhouse. Any clothes or shoes left out there get moldy. On my long list of house projects is to make it an insulated, conditioned mudroom.
I always thought the purpose of the mudroom was to provide a buffer between the muddy outdoors and the clean indoors, and often mudrooms are where washing machines, closets, boot and coat racks, and half bathrooms are placed, for that purpose. An arctic entry is closer to the airlock concept, definitely not a foyer, and is usually heated, but kept colder than the interior space. Every arctic entryway I've seen has a heater positioned under the coat rack and adjacent to the boot rack to promote drying, and its main purpose is for shedding those snow-covered or wet boots and coats before coming into the clean, dry, fully conditioned space. It also does eliminate blasts of cold air from the outside and can help keep pets from getting out. Whether it's more thermally efficient somehow always seemed moot.