Breeze Blowing In

[mkgrady]

I have a customer that has air blowing in through the outside walls through receptacles and switches. She lives right on the coast so the wind gets pretty strong. The walls are wood studs, plywood sheathing and drywall with fiberglass insulation.

She tried using those foam pads that fit between the plate and the device but it does a poor job of slowing down the air.

She had a insulation installer check it out and he recommended she spray foam insulation in to each device box on exterior walls. She asked me what I thought and I said it sounds wrong to me.

Anybody ever hear about this fix? If this method doesn't make sense, as I suspect, does anybody know of a good way to slow down the air?

 

[iwire]

Spray foam in the wall behind and around the box not in the box.

 

[mkgrady]

Spray foam in the wall behind and around the box not in the box.

I'm trying to picture how to get the foam in the wall cavity around the box. The can comes with a pretty small straw like tube. Are you saying make a small hole just right above and below the box?

 

[Redcliffe]

I would insert the tube between the sheetrock and the box and spray away. if you have to widen it do so and if it violates code, use a box extender. we have all come across boxes
that have more than a 1/4 inch between sheetrock and box.

 

[qcroanoke]

I would insert the tube between the sheetrock and the box and spray away. if you have to widen it do so and if it violates code, use a box extender. we have all come across boxes
that have more than a 1/4 inch between sheetrock and box.

I don't think I would spray away. The foam expands quite a bit and you don't want to damage the drywall around the box. Just a little to see how much it is going to expand.

 

[gadfly56]

I'm trying to picture how to get the foam in the wall cavity around the box. The can comes with a pretty small straw like tube. Are you saying make a small hole just right above and below the box?

Depending on the make and model of the box, there might be holes in each surface you could feed the straw through. Alternatively, you might drill some small holes yourself, although that might be some sort of violation of the box's listing.

 

[jumper]

I would insert the tube between the sheetrock and the box and spray away. if you have to widen it do so and if it violates code, use a box extender. we have all come across boxes
that have more than a 1/4 inch between sheetrock and box.

Gap width is 1/8th inch and I do not believe that a box extender covers that type of gap. Extenders work on depth gaps.

1/4 inch is the allowable setback of a box in a non combustible surface.

 

[mgookin]

Are you sure there is airflow?

She very well could just have cold spots (from less insulation where a box is) and those cold spots could create the perception of a breeze.

 

[mkgrady]

Are you sure there is airflow?

She very well could just have cold spots (from less insulation where a box is) and those cold spots could create the perception of a breeze.

Good point. I'll have her hang a square of tissue over the box to see if it moves with the wind. Even if it is not wind I assume the foam would reduce the heat transfer.

 

[ceb58]

I agree that foam would be the way to go but I think I would use the fire rated foam around the boxes instead of something like "great stuff".

 

[John120/240]

Use low expanding foam. If you need to make little holes around the edge of boxes, use a Jumbo plate to cover up your holes.

 

[gadfly56]

I agree that foam would be the way to go but I think I would use the fire rated foam around the boxes instead of something like "great stuff".

Great point, but you're too quick to write off Great Stuff. They make a product for fire block. See here.

 

[kwired]

Sealing penetrations into the wall cavity where wiring enters (if you can access them) may be a big help.

Sometimes depending on construction methods the wall cavity may not be sealed off either. Most newer construction methods however does seal wall cavities and they do foam any penetrations before finish materials are installed to make the wall as air tight as they can.

If you want to shoot expanding foam into the wall with the intention of encapsulating the box, maybe use low pressure expanding foam so you don't blow something out from the foam pressure.

 

[FREEBALL]

I agree with the low expanding foam but am curious as to why you would need fire block on an exterior wall normal low expansion foam would be adequate. I was over thinking this and thought about using a scope camera and foam, ofcourse you would have to drill holes in the wall around the box but would give a good idea where your spraying.

 

[cuba_pete]

Increase Pressure

Increase Pressure

Insulating is a great idea to keep the cold spots to a minimum.

If air is flowing from the outside into the home due to wind induced or negative pressure, it could be a function of the forced air cooling or heating, woodstove (venting), gas appliances, stove vent hoods, recessed lighting, attic ventilation, etc. as well. By increasing the static pressure of the home's interior it will greatly reduce or eliminate airflow into the home through the unintended paths. Blocking one requires blocking them all. The air will find its way through the weak areas.

 

[GoldDigger]

Insulating is a great idea to keep the cold spots to a minimum.

If air is flowing from the outside into the home due to wind induced or negative pressure, it could be a function of the forced air cooling or heating, woodstove (venting), gas appliances, stove vent hoods, recessed lighting, attic ventilation, etc. as well. By increasing the static pressure of the home's interior it will greatly reduce or eliminate airflow into the home through the unintended paths. Blocking one requires blocking them all. The air will find its way through the weak areas.

But if you close too many of the air infiltration sources, you may increase the internal negative pressure to the point that flame sources like furnace, wood stove, or water heater do not get enough draft and become s CO hazard.
You may then need to provide deliberate makeup air inlets for them in a way that does not produce drafts.

 

[kwired]

Insulating is a great idea to keep the cold spots to a minimum.

If air is flowing from the outside into the home due to wind induced or negative pressure, it could be a function of the forced air cooling or heating, woodstove (venting), gas appliances, stove vent hoods, recessed lighting, attic ventilation, etc. as well. By increasing the static pressure of the home's interior it will greatly reduce or eliminate airflow into the home through the unintended paths. Blocking one requires blocking them all. The air will find its way through the weak areas.

Good points there as well, if you are exhausting air someplace then makeup air must come in someplace. Used to be homes were not so air tight that this was a problem, but anymore we do seal them better so when intentionally removing air you need to have makeup air of some kind or it will find every place it can to try to use for makeup. It often is worse with commercial exhausting systems as they often move even more air. Ever go to some places where the front door pulls really hard until it has "broken the seal"? That is a place that doesn't have sufficient make up air for an exhaust system.

 

[mgookin]

Makeup air is for when you have an exhaust fan, namely a commercial kitchen hood, which does nothing more than exhaust air. You provide makeup air per the mechanical code, which usually calls it balanced air. Whatever CFM's you exhaust, you shall "makeup" with an air inlet (fan forced). This way we're not messing up other systems (a/c or fossil fuel burning appliances).

When it comes to CO we need combustion air under the fuel gas code. That requirement makes sure you have ample airflow for combustion to get a clean (efficient) burn and to exhaust the CO and other products of combustion.

 

[kwired]

Makeup air is for when you have an exhaust fan, namely a commercial kitchen hood, which does nothing more than exhaust air. You provide makeup air per the mechanical code, which usually calls it balanced air. Whatever CFM's you exhaust, you shall "makeup" with an air inlet (fan forced). This way we're not messing up other systems (a/c or fossil fuel burning appliances).

When it comes to CO we need combustion air under the fuel gas code. That requirement makes sure you have ample airflow for combustion to get a clean (efficient) burn and to exhaust the CO and other products of combustion.

Any air leaving an enclosed space needs air to replace it or you have negative air pressure - hence my calling it make up air. Combustion air may very well be a defined term in fuel gas code, but we are elecricians here

 

[handy10]

Making a small hole beside the box is a good idea, but around here most boxes are 4x4 with a mud ring that may reduce the size of the wall opening to single gang. Then the hole will be outside the cover plate. Why not use the existing holes in the box to inject foam as someone suggested?