How would *you* build a north wall that faces a fire station across the street?
user941025
| Posted in General Questions on
An urban infill question.
Starting from scratch, if you had a lot across the street from a fire station–beyond (presumably) “windowless,” how would you build your north house wall which faces that station?
Since the inverse square law is relevant: when the trucks pull into the street, that siren probably is 10-20 yards away.
Curious to read your responses.
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The north wall is probably a good candidate for masonry construction, the denser the better. ICF etc. If not that, dense-pack cellulose in an 8" or thicker stud wall would be a good start. Add to that two layers of sheetrock on the inside with staggered joints.
The bigger question is the planning of the building itself:
a) to minimize sound impact on the most important rooms, use ancillary and active spaces like laundry, kitchen, bathrooms, mudroom etc as buffers (a few small triple-glazed windows in those rooms will be OK).
b) create a shielded backyard area where siren noise will be minimized. An L shape in particular can help create a relatively protected corner. Dense sound-absorbtive plantings in the side yards will also help.
Minneapolis,
The answer depends on the circumstances of the site. How close are the neighbors? If the east and west walls of this infill site have zero setback, or share a common wall with adjacent houses, you obviously need north windows. Even if you have 10 feet between the proposed house and the houses to the east and west, privacy concerns often preclude large windows facing the neighbors.
If you are worried about sound transmission, you obviously want triple-glazed windows.
As stated a L or U shape will create a noise break for the back of the house.
A concrete block wall in the front yard could create a courtyard on the street side and
a buffer before the sound gets to the actual house. ICF out preforms most other wall types for sound.
I looked a while back at the Canadian study on various wall assemblies and SPL dampening that was linked in a blog post here, but don't remember if there was an ICF component.
I'd previously assumed 12" double stud walls with a double layer of 5/8" gypsum to the interior and of course gaskets or caulk, so pretty much in keeping with the non-ICF approach James mentions above.
If ICF is crucially important in really blocking that sound in a way thick double-stud walls just can't, I'd be interested in knowing that for sure.
(And of course dealing with anywhere the building flanking to the side would bounce it back at the house--same approach. Agreed on your points--thanks for noting it.)
Would it be worthwhile to hang the drywall on resilient channel?
If you are primarily concerned with blocking high frequency noise from sirens, then the extra mass of ICF or masonry would not be necessary for good results. Mass helps to block low frequency sound energy, but soft materials (such as dense packed cellulose) can effectively absorb high frequency energy.
TJ, Good to know about dense pack cellulose blocking high frequency.
I lived down the street from a fire station and its not just the sirens.
They are big, heavy trucks with big diesel engines.
They were loud, but it didn't take long before they were out of range.
Fire truck sirens are not like police sirens. At least down our way they generate enough bass to make a low-rider jealous. There's a fire station just down the street from my office and when those big babies come by they make the windows rattle.
But you can still do a good job with cellulose. Don't bother with resilient channel, that's for dampening impact noise, like footfall on an upper floor. Impeccable air-sealing (you'd be doing that anyway, right?) is going to be critical - sound energy takes the path of least resistance from one side of the wall assembly to the other. Flanking transmission through the ceiling is going to be a factor, take special care to have sufficient insulation and proper blocking at the wall/roof interface: raised heel truss etc.
Oh, and those triple-glazed windows should be fixed, awning or casement units with compression seals, not double-hung or any other kind of sliders.
I know that the focus of this forum is technical rather than aesthetic, but It's important to keep in mind side effects that otherwise sound practices can have.
Are we talking here about making the entire front of the house a windowless and possibly masonry wall? Such a feature will be tricky to design so that it looks good. And many communities (including Minneapolis) have rules requiring a certain percentage of glass on the front of a house. Be sure to check out design restrictions with the local planning department. Triple glazing and placing less noise-sensitive rooms on the north side may be your best option.
Whoops! I missed the "beyond" in the initial post - obviously Minneapolis is not seriously planning the faux pas I was worried about. Still, keep in mind the local rules when minimizing window area!
Thanks, Jody--yep, I've dealt with the minimum glazing ordinance before. Meeting 15-20% minimum glazing on each floor, to the north, plus a fire station right there...