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passive solar

Florida conversion

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posted 1 year ago

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I've been reading about passive solar building designs that can help to promote cooling. However, I haven't found anything dealing with retrofits. Beyond that, I doubt there is much that I could DIY comfortably. I'd really like to find an expert in south florida to work with. Any ideas concerning where I could start?

Matt McSpadden

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Hi Mike,
I'm no expert in passive design, but you might see if there are any companies that work with Passivhaus or LEED. While I don't really agree with how they achieve some of their ratings, a company that works with those certs will probably be more open to alternative designs than a traditional company.

Generally speaking you want to increase your insulation and reduce your sun exposure. Make your eaves longer, make your windows smaller. Double your insulation. Those sorts of things would go a long way to helping your house, and could be retrofitted fairly easily.

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Anne Miller

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Matt McSpadden wrote:Generally speaking you want to increase your insulation and reduce your sun exposure. Make your eaves longer, make your windows smaller. Double your insulation. Those sorts of things would go a long way to helping your house and could be retrofitted fairly easily.

I agree with the double insulation and making the eaves longer.

My house was someone else's dream for passive solar.

There are high windows on the east and west sides of the house. Large windows were placed across from each other on the north and south sides. All of this was for cross-ventilation.

There are no windows on the east side except those high windows and only one large window on the west side near the south side.

I hope you will find a contractor.

Here are some links that might offer something of value to you or others:

http://www.phys.ufl.edu/~liz/design.html

https://www.nrel.gov/docs/legosti/old/17178.pdf

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Mike Benjamin

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posted 1 year ago

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Thanks for your responses. I agree with the importance of insulation and shade produced by longer eaves (balanced against updraft risk from hurricanes). Granted, in the summer at my latitude, the sun is mostly overhead, so I think that getting a metal roof next time and upgrading the insulation further (have already made improvements there) will make a big dent.

Though I'm also trying to understand more strategies, like those linked by Anne. I have read those pages before. The cracker house project was super interesting and I appreciate how well it was detailed. Though it is useful for building from scratch, how to incorporate the ideas into a retrofit is difficult.

I'll take the advice of at least reaching out to some LEED certified contractors and see if they can steer me in a productive direction.

Thank you

John C Daley

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Mike, you are complicating the ideas.
I suggest you create a drawing of your existing home and then add 'passive' concepts to the drawing as you think they apply.
Perhaps use tracing paper, slowly the ideas will form.

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Matt McSpadden

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@Mike,
Another thought I had after you mentioned replacing the roof, is to get either a light color roof, or one that has a reflective coating. Reflecting the heat away will also help.

Anne Miller

steward

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This article suggests that "A passive solar system consists of only five basic components." The article goes on to list what those 5 components are.

Basically, the gist of the article suggests adding a sunroom to an existing home to make it passive solar.

In Florida, I have seen lots of homes with sunrooms many times enclosing a pool.

https://www.offthegridnews.com/grid-threats/how-to-convert-your-home-to-passive-solar/

Invasive plants are Earth's way of insisting we notice her medicines. Stephen Herrod Buhner
Everyone learns what works by learning what doesn't work. Stephen Herrod Buhner

Mike Benjamin

Posts: 78

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Anne Miller wrote:This article suggests that "A passive solar system consists of only five basic components." The article goes on to list what those 5 components are.

Basically, the gist of the article suggests adding a sunroom to an existing home to make it passive solar.

In Florida, I have seen lots of homes with sunrooms many times enclosing a pool.

https://www.offthegridnews.com/grid-threats/how-to-convert-your-home-to-passive-solar/

Thanks again for the comments, everyone.

The article linked, Anne, deals with passive heating. This is the trouble I run into. It's hard to find anything that addresses cooling. One obvious point is that, all year round, I want to keep the sun out of my house.

I wonder if thermal mass plays a role for me? Do I want to have thermal mass to soak up the heat during the day and then open my windows and vent it out at night? If so, this would go along with something that would be very expensive to try to install without expert guidance concerning its efficacy: a solar chimney. A whole house vent fan isn't passive, but could work.

I agree with the reflective roof. My next roof will be metal - common in my area as they are long lasting and good for hurricanes. Very reflective. However, that won't be for a while. I was looking to get solar panels installed to provide shade over certain rooms, but my insurance won't allow it.

Matt McSpadden

gardener

Posts: 2217

Location: Central Maine (Zone 5a)

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@Mike,
I agree the passive solar heating might not fit your needs :)

I just keep thinking of buildings from areas that get hot. Adobe style in the southwest US - thick walls of insulation material. Huts with big overhangs in the Caribbean - blocking direct sun.

I suppose another thing could be plant shade. While trees would take some time to grow, I suspect you could get a tall trellis or two in front of some south facing windows. Put some fast growing vine-y plants on them.

Mike Benjamin

Posts: 78

posted 1 year ago

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To follow up on this point, I wonder if anyone can help me with this issue...

I have a room with vaulted ceilings. I got a new roof 2 years ago (shingle unfortunately. I wasn't aware at the time that I should pick a reflective material. Will address it in the future, but that's not for a while). When I got the new roof on, we realized that the ceiling was the bottom of the roof sheathing! There is zero insulation (the sun was shining through into the house). To get this room insulated I would either need to spray foam (which I don't want to do. I don't want to live in a recently spray foamed house due to fumes/off gassing) or insulate above the roof. Insulating above the roof would require pulling off and trashing the shingles. It would also cost a pretty penny ($15,500). But it would make my house a lot cooler. Any thoughts on this situation? I could wait obviously until I re-roof to insulate (and I would put on a reflective roof), but that won't be for like 15 years.

Matt McSpadden

gardener

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Location: Central Maine (Zone 5a)

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Hi Mike,
I don't think those are your only options. Especially if it is a vaulted ceiling.

One option would be to add another set of studs under the ones that are there, and then insulate between as normal using something like rockwool (easy to find around here) or something made out of sheep's wool or hemp could also work. It would lower your ceiling a little, but it would insulate and be way cheaper than 15k.

Another option would be to use the rockwool board (similar to those 4x8 sheets of foam, but more environmentally friendly I think), and tack those up and cover with some light weight paneling or something. Can you post a few pictures? That would help to be more specific.

James Alun

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So at once place I lived there was a flat roof and the upstairs exterior walls were tiled (fake cement slates).

I painted the slates with normal exterior paint and fitted rigid insulation board between the 2"x2" joists and then covered that with polystyrene backed plasterboard.

This massively cut down on the extra heat gain in summer and made it a bit more pleasant in winter. If I had more ceiling height I would have used fibre insulation but what I did only lower the ceiling by 70mm.

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Mike Benjamin

Posts: 78

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Thanks for the replies. Unfortunately, I can't see how to post an image. I have some comments in response to the replies.
First, unfortunately, since the roof is shingle, I can't paint it. That was the first thing I looked into. As I understand it from my research, shingles need to breath and paint can adversely affect them.
Second, in terms of the insulation without using spray foam.. my understanding is that I would need it to be vented (which is currently is not), since moisture can get trapped between the insulation and roof sheathing, causing it to rot. I read about this in the following article, which is either now behind a paywall, or is paywalled to me because I maxed out my free reading on the website: https://www.greenbuildingadvisor.com/article/how-to-build-an-insulated-cathedral-ceiling

Staff note (Clay Bunch) :

Here is a link to help with posting an image on permies.

https://permies.com/wiki/61133/Post-Image-Permies#1770553

John Ian Smith

Posts: 16

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Here's a list of approved PV system installers, they may offer advice about using passive systems for your application. https://www.bls.gov/ooh/construction-and-extraction/solar-photovoltaic-installers.htm

However, if you choose a non-approved contractor, you may want to do a free background check on their company. I found this that shows you how to do it in Florida: https://backgroundcheckrepair.org/background-check-florida/

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