Retrofitting home in south Florida

Hi all. I made a post in alternative building about this and we had some good discussion. I live in a home that is very standard for the US - entirely dependent upon air conditioning to maintain even modest levels of comfort and to prevent the build up of mold due to the high humidity. My house is made out of concrete block. I don't have any windows in my home that are opposite each other (though I do have a ton of windows). I've done some basic research into how buildings are designed in the tropics to promote passive cooling (or at least keeping things from getting too hot). But I haven't been able to successfully apply those ideas to retrofitting an existing home in my climate. There is always the obvious: reflective roofing material, insulation, and shading windows and walls. Other than those basics, does anyone have any insights to offer? Thank you.

A moisture barrier under the floor perhaps will reduce molds.

Most concrete block houses in the tropics don't grow mold, esp on the islands, so I don't think that you need anything special for mold.
You could spend most of your time outside on a covered porch/tree/etc with wind blowing, maybe on a hammock.
Personally I am not a big fan of AC because once I get used to 75F at 50% humidity there is no way I am going to spend time outside in 90F and 90% humidty it is just too much of a shock to my body. But if I just let my body get used to 85F-95F. I don't really notice the huge difference and I end up spending more time outside and being active, drinking more water, sweating more and just being healthier.

S Bengi wrote:Most concrete block houses in the tropics don't grow mold, esp on the islands, so I don't think that you need anything special for mold.
You could spend most of your time outside on a covered porch/tree/etc with wind blowing, maybe on a hammock.
Personally I am not a big fan of AC because once I get used to 75F at 50% humidity there is no way I am going to spend time outside in 90F and 90% humidty it is just too much of a shock to my body. But if I just let my body get used to 85F-95F. I don't really notice the huge difference and I end up spending more time outside and being active, drinking more water, sweating more and just being healthier.

I couldn't agree more with the implications of AC. We use AC (because it isn't just me imposing my decisions on my family of course - my wife wants AC) but we set it high. Our living room where we hang out tends to be around 80 degrees or so. Living an outdoor-based lifestyle, in my view, is very important and too much mechanical cooling inhibits that.
With the concrete block - only the exterior walls are concrete block. Interior are not. Is that how your house is set up, or is yours concrete block all the way through?

Mines is concrete for all interior and exterior walls, everything is concrete even the roof was converted to concrete, this house is on the islands. It helps that it is a owner-builder house. Right now I am in Boston and everything is wood framed and dry wall. I prefer the simplicity of an all concrete house. I do have a few acres of land in SouthWest Florida/ Fort Myers. I need to get more fruit trees on it, and now I am here thinking about what type of house would best fit that. All concrete or build from bamboo, that needs to be refreshed every decade or so.

You could get 3inch of foarm that is 40ft by 10ft, then cut out doors/etc and then spray stucco/gunnite on it for interior walls.
https://www.youtube.com/watch?v=VJekgKmro_Y

I like your current setup of just taking the edge off the temp, but not to the point where it would shock your body to go outside. For mold maybe you could get a ozone machine and just run it once a month. And then the usual of venting the bathroom and kitchen during use.

Hey Mike,
I've been thinking about your house a lot the last few weeks. If you had the opportunity to create an opening up high in a room with windows, I'd expect it could help vent hot air and draw in outside air.

Growing up in (and returning to) a hot humid climate, I can empathize with you, and I believe, both personally and professionally, that a bit of air movement goes a long way to the perception of comfort in our hot/humid climates.

there's always the porch effect as well- shades those walls, and gives you a nice place to chill in the shade around the house. also a place for shade-creating vines to grow. We built porches on the front and back, blocking the direct sun, and it makes an amazing difference.

I live in a block house in the almost-tropics with no AC and we do get some mold, but we also get colder than pretty much any other place in this country. We run a dehumidifier when things are a bit too humid. We also use a special impermeable coating at ground level and below to help with infiltration/mold.

The opposite window thing is absolutely key, as is having a nice tight house (as S Bengi mentions, all concrete block or brick, even concrete block ceilings under the tile roof) built on a concrete or earth pad. My house is cool in the summer, perhaps a bit too cool in the winter for my taste, but we almost never even run fans, and have never even considered air conditioning.

This lady built a building around her mobile home to protect, heat & cool the mobile home.

I wonder if a sort of passive solar deck could be built around a concrete block home to retrofit the home into something passive solar?

https://permies.com/t/58007/Mobile-Home-Building

Very interesting suggestions. Thank you all. Some are not workable as I'm in an HOA. It's not a very overbearing HOA at all, but I don't see them approving a new roof over my current roof

With that said, there's a lot of actionable points to consider and I'm grateful for the feedback.

@S Bengi - if there is the chance you could get stuck in that house during a hurricane without the ability to evacuate, go with concrete! We planned to evacuate for Irma, but by the time we were going to head out, everyone north of us in the state started evacuating as well. Roads were jammed and fuel was too unreliable to risk leaving and being stranded. Fortunately for us, the storm turned north later than expected.

@Ash - I'm guessing you're pretty far south in Miami to be at zome 11A? Homestead maybe?
As I've been researching this issue, it seems like I could get good airflow by capturing the breeze coming from the east south/east, and letting it exit at a higher point on the west north/west. My family, living room, and kitchen is oriented within about 20 degrees of east to west, perfectly set up to capture and move breeze. The room on the west has a vaulted ceiling, so I have a high point to let the air out - I just need to make sure I can seal it up tight for hurricanes. The major change would be that I'd need to open up the wall between them, which sacrifices storage space in the kitchen, but that's a tradeoff that would probably be worth it. I'd consult with an architect who could help to model the impact of this retrofit.
The other rooms in my house are off of a north jetting hallway. Passive airflow back there is much more difficult. However, perhaps a pocket door can help to keep the hot humid air from entering the mechanically cooled/dehumidified air in that section of the house.

Mike Benjamin wrote:Very interesting suggestions. Thank you all. Some are not workable as I'm in an HOA. It's not a very overbearing HOA at all, but I don't see them approving a new roof over my current roof

I am not sure I saw where someone was suggesting a roof over your existing roof as that would be way too expensive.

I am hoping all this discussion has helped you make some changes.

The mold spores are in the air and dust, so wherever they accumulate is where the mold forms (combined with the high humidity)

A HEPA filter installed on the A/C return air duct can capture a lot of these microscopic spores and also help you to breathe better by removing allergens.

A whole house fan that draws out the warmer and more humid air layer from above your head can be very effective, combined with better attic ventilation will cool the house and also prevent roof rot.

Not a big fan of block houses, but in Florida they make the most sense and the humidity will be high either way. For your out of the way spots in your house that are not well ventilated, the small canisters that draw moisture and get drained periodically, work really well.

Luckily the sandy soil drains quickly, so its unlikely that moisture is wicking upwards like in some wet locations with clay soils. And of course its always more efficient to find a temp on the A/C that you can live with and leave it there, rather than turning it up and down. The dehumidifying effect is at least one free benefit to that...