through-wall AC install

[JHZR2]

We are replacing a through-wall AC that is in our living room with a quieter, lower BTU unit that will be part of our new overall air conditioning scheme.

It is in the back of the house so it is not in sight, and it was determined that keeping a wall unit (we will not be going central for a number of reasons) was the best approach.

Ive heard that perhaps it is smart to put a piece of rubber sheet on the frame around where the AC will be installed, to help absorb vibration. This seems sensible, though I doubt our current unit has it, and though loud, it does not vibrate in an offensive way.

Is doing that a sound approach? If so, what should I use, say, 1/8" rubber sheet?

Thanks!

 

[OtisBlkR1]

first time ive ever heard of anyone doing this.. (using rubber) although i know several that have used foam insulation 100% around and under the A/C with good results.

 

[Lead Shoes]

My parents use some rubber stripping like that around the window unit upstairs to reduce vibration and seal it in, 1/8 should work, but I believe theirs is 3/8" rubber, it works well, defiantly a good DIY.

 

[JHZR2]

Originally Posted By: OtisBlkR1
first time ive ever heard of anyone doing this.. (using rubber) although i know several that have used foam insulation 100% around and under the A/C with good results.


What kind and where? Any ideas?

Are you saying that the AC chassis was sat on the foam?

 

[abycat]

I agree 100% use something not too hard and still suspends the unit of off the frame. It has too make more noise from resonance. You might not think you hear it but i know its there.

I use foam on the bottom only and i have very quiet rooms. As i type my 8000 btu unit is going and i have to strain to hear it over the fairly low tv. And its 10' away from my head. Its about 7' from the wifes. Cheapo units as well.

If i didnt use the supplied foam which works good id try a hobby store or craft store. Id say a foam a little more plyable than styrofoam but dont use styro its too hard and squeeky.

 

[daves87rs]

Some cheap rubber, maybe?


Thought about doing wall units myself (doing it here until the end of summer, but central air seems to work much better here...

 

[Carbon]

You will probably need to cut a stud. Make sure that you heavily reinforce the frame area to make up for this. I would put 2x4s or bigger above and below all the way across between the uncut studs. I would use glue and screws on the left, right, and into the remnants of the cut stud.

Make sure you don't have a tilt toward the inside.

I would not use rubber. I would use strong construction. This method requires some drywall work. It is hard to get enough wood on the job otherwise.

 

[abycat]

Not rubber cause that will squeek as well. And will transfer vibration to the walls. Foam is the best. I have to sound proof stuff all the time.

 

[JimPghPA]

Mount the AC unit so it is well installed, and then put about 50 Pounds on top of the outside section to reduce vibration. We had a big unit in our living-room, and a metal 50 pound weight from a barbell set on top of the outside reduced the noise it was making.

More recently I installed a new 8KBTU unit in a window and used two tubes of outdoor rated liquid nail to glue ten red-bricks to the top of it to reduce the vibration. That unit is also well secured with four cables combined with S hooks and turn-buckles.

There was a recent article about how all window and casement units are short on supplying the actual rated BTUs. So if you want for example a true 10KBTU and you think that 9.5 BTUs might be to small then go up one size.

Also I ran the unit in the store to see how quiet it was, but sitting on the carpet on the floor of the store was apparently not a good way to determine the noise it makes.

The most noticeable noise I am having with this new unit is that compared to the unit it is replacing it allows way too much noise to pass directly through the AC unit so that noise from outside is heard inside, and noise from inside is heard outside.

The older unit was much heavier and a little bit bigger. It let just about no noise transfer from inside of house to outside, or from outside to inside.

This new unit also lets in sunlight. Apparently there is a translucent plastic barer in the air flow passageway that lets light from outside show through. I think this is also the pathway for noise transfer.

I bought the new 8KBTU window unit as Sears. If I had it to do over again I would not get that unit.

 

[JimPghPA]

If you put weights on top of the AC unit be suer to not block any vents if it has any on top.

 

[JHZR2]

Originally Posted By: abycat
Not rubber cause that will squeek as well. And will transfer vibration to the walls. Foam is the best. I have to sound proof stuff all the time.


Any suggestions as to the type of foam? I was thinking a 70-ish durometer rubber sheet, but if foam is better (and will last), then so be it.

 

[bigmike]

I've put in some through-wall A/C units and I've always shimmed units with composite shims to make sure the unit is level (slightly pitched back for water run off would be a consideration as well), then using spray foam insulation around the unit. Once the foam is set up and cut smooth, I put some trim around the inside to cover and some pressure treated trim outside.

 

[LeakySeals]

I use cut up rubber flooring squares or floor mats. They can take the exposure.
http://www.homedepot.com/h_d1/N-5yc1v/R-...51#.UBE4X6BFnMo
http://www.homedepot.com/h_d1/N-5yc1v/R-...51#.UBE4-qBFnMo

Speaking of schemes, I just swapped my wall units out for this..
http://www.google.com/search?tbm=shop&am...1ac.dQMhBFTyky8

Its like central AC/heating, without the ducts. More initial cost, but no noise, energy bills go down, and I have multiple vents dampened for better efficiency. You can find deals with local installers, but the link above gives you an idea about them.

 

[LeakySeals]

PS: The other option is to reinforce the sill. The AC is probably sitting on a couple of shims with a gap, a single 2X4 with a couple of 2X4 supports. Beefing that up will cut vibration without the eyesore rubber, but requires cutting out the sheet rock, a patch and a repaint. You may be able to get to the gap removing the window trim. An expanding rubber compound in there may be all you need.

 

[river_rat]

Sounds like a good idea. I assume you have hot water heat in NJ? No ducts definitely complicates central air, but they have systems for doind so with the small, flexible, high velocity ducting--expensive though.
My wife won't let me put on through the wall in the master bedroom so we can turn up the temperature for the rest of the house at night. As long as the unit is quiet, I like being able to control each room independently without messing with the register dampers.

 

[JHZR2]

Leaky,

Those splits are our preferred approach for most of the house!!

When you took those rubber parts for install, I assume you lined the whole lower sill of the hole in the wall with it? What about top and sides?

The hole is already there and sturdy. I don't get any wall-borne vibration, but my hope is that I can minimize noise any way I can..

 

[LeakySeals]

I've tried all different ways, directly under the AC on the sill and the top where the AC locks into the closed window were the only difference makers. Cut a piece larger than needed. Get it in place, test, then cut of excess with a razor blade for aesthetics. Be careful with the top rubber, Id use a couple of screws through the window and rubber to secure it.

 

[mechtech2]

Make sure the unit is angled back for drainage.
A rubber sheet should help with vibration/noise.
Don't block drain holes..

 

[morris]

just an idea use the rubber to rout any water away from the house. buy making the rubber longer out to the outside.