Need advise on wall insulation (thanks!) (how much, house, transfer)

[behtypa]

I have 2 issues, that I hope to resolve by using a spray-foam insulation. Please tell me if it's a good idea.

Issue 1. My Southwest wall in a master bedroom gets really warm (+3deg), especially in summer.
The sun path is right above that wall, so it heats it up during the day. The A/C helps, but the wall R-15/30 batt insulation is probably not enough to block the heat transfer.
Issue 2. Warmer wall attracts ants. We do treat insects, but they tend to live around the warmer wall and scout ants come in frequently.

The wall on the outside is a combination of brick with weeping holes. On the inside it is a framing + 1 layer of styrofoam + R15 batt insulation + sheetrock.



I hope 1 inch of spray-foam insulation would insulate all crevices from the inside making it impermeable to ants. Secondly, it would be impermeable to the heat transfer. I would sandwich it with R15 on top and cover with sheetrock.



The potential negative to using a spray-foam is that it may block the weeping holes. There will be a styrofoam sheet in between. Correct me if I am wrong.

What are other cons to using spray-foam insulation?

Overall, what method would you use to block the heat transfer from warm brick wall on the outside + ants from coming in?

[escanlan]

If I understand you correctly you are going to remove the interior drywall, remove the cavity insulation, leave the Styrofoam sheathing, then replace the batt insulation with spray foam insulation? If so the Styrofoam sheathing will act as the backer to prevent the spray foam insulation from entering the cavity between the sheathing and brick.

The spray foam insulation can provide some reduction of the heat transfer and will certainly seal it off much better from air infiltration than batt insulation. It will not make the wall "impermeable" to heat transfer and you will still have heat transfer through the wall but to a lesser degree. How much "lesser" can be calculated but not guaranteed. It is a relatively expensive option to reducing the issues of heat on that wall.

On the wall you are having problems with are there windows or is it a solid wall? What is outside of this wall and what is across from it (across any yard or opening?

As for ants this will never stop them from entering the home. If they can not enter at that wall point they will enter at another nearby. They can also enter the brick cavity and obtain the same things they are looking for and eventually make their way around to another home opening.

[marksmu]

I agree with previous poster. Remove the styrofoam and just use spray foam straight against the plywood....Sprayfoam is not a "superior" insulating material unless it is applied to the wood to fill the gaps. What makes foam outstanding is that it fills all the holes that normally allow air to penetrate and cause drafts.

My whole house is spray foam and it is outstanding - but you only get the advantage if you seal the whole envelope. Otherwise it is not any better than fiberglass batt insulation. In fact, batt has a higher R value than most spray foam, so unless you get the advantage of sealing the envelope of the home, dont bother with your plan.

[behtypa]

Two posters, below: Thanks a lot for detailed explanation. Much appreciated.