Greetings from Houston. Glad I found this site with such a wealth of knowledge.

My wife and I are several months into an empty nester project. It’s a small house in Galveston built in 1886 that survived the 1900 hurricane and was raised … now has a 6′ crawl space underneath. More on that later. And FYI for those not familiar with Galveston…it is insanely humid.

I apologize in advance for the novel but want to be thorough.

We are converting the attic into a conditioned third bedroom with a powder bath and I’m looking for insulation advice.

We are surrounded by some beautiful / restored Victorians and have met a ton of great neighbors. I have been blown away at how many of these homes … with the exception of batt on the attic floor … are not insulated. All of these homes (including ours) were constructed with cypress and built to breathe. A common theme is “Sealing air gaps helps but we bake in the summer and freeze in the winter with high power bills.”

The downstairs walls are tongue and groove. I’m not going to touch them…they will remain uninsulated.

When we purchased the house, it had old fiberglass batt between the floor joists and an old door with a pulley covering the stairs leading up to the attic. This and all the old batt have been removed as well as the old wiring, etc. in the first picture.

With the exception of air gaps in the siding there was no attic ventilation. We recently had a new roof installed. There are now 2 Air Hawks on the East side. My wife shot down Air Hawks on the West side due to aesthetics.

Spray foam makes me nervous due to lingering smell / mold horror stories I have heard. No offense whatsoever to foam advocates of course. I’m just viewing foam from a last option lens as it stands.

A contractor friend told me to just insulate throughout with fiberglass batt or mineral wool and be done with it.

I’m fine with fiberglass batt between the floor joists outside of the knee wall.

The rafters, knee walls, and North / South walls will have drywall.

Regarding the rafters … they look bigger but are 2×4… and I know there’s no way to get max R-value against the roof due to dimensions.

1. Batt and drywall be done with it?

2. Combine batt with vapor barrier against the ceiling?

3. Batt with 1/2″or 1″ Polyiso or XPS snug / flush with rafters and sealed and then drywall directly against the Polyiso or XPS?

4. Paint roof facing side of drywall with RedGard?

Regarding knee walls…I can of course install batt with much higher R-value.

1. Paint RedGard on hot side of drywall with batt directly against drywall?

2. 1″ Polyiso or XPS flush and sealed against studs with drywall directly against and batt on hot side?

3. Something else?

Regarding North / South exterior walls … you can see that wind driven rain has been blown in over the past 139 years … and due to the spacing / cavity the cypress siding just dries out with no signs of rot / mold. I’m hesitant to fill the entire cavity with insulation.

1. I know I would lose R-value … but what about 2″ Polyiso or XPS flush and sealed against studs? This would leave an air gap so the siding can continue to dry out.

2. Mineral wool in the entire cavity…doesn’t absorb water and would provide higher R-value?

3. Vapor barrier with either scenario?

4. RedGard on hot side of drywall with either scenario?

I don’t mind spending extra money for any proposed scenario…and will be slow and meticulous with the installation.

Last question…would you guys recommend exhaust fans on both sides? My wife has given the green light with decorative gable vents.

Sorry again for the long ramble…beat up my thoughts…I won’t get offended…and look forward to the input.

Mark