New home in Orlando…lots of questions
Hi all, signed up today and will be doing a lot more reading. I had previously built an ICF house back in 2007 with Icynene open cell to seal the roof/attic (which was apparently a mistake).
This go around, I will be using the ICF again (likely Nudura), but am really struggling to understand the attic insulation. I’ve got the floor plan laid out and decided to use ICF for the 2nd floor too. For the cost of insulating the upstairs walls, I decided the strength and sound are hard to beat even if it isn’t max insulation. For the attic insulation, I’m leaning towards a few inches of closed cell and then I’m not sure what to do to increase the R value, or even what R target makes sense in Florida (light colored metal roof).
As for HVAC, I had a zoned system in the old house and had a love hate relationship with it, so this house will have multiple units. I’m looking for a good HVAC designer and think I stumbled across Energywise on this site at some point, but open to other suggestions. It seems the options for the attic are to feed some conditioned air or use a dehumidifier if my research is correct. The dehumidifier makes more sense in my mind, especially for Florida… I also plan on conditioning the garage, but not sure if I should do something different with the insulation out there since it is not a shared attic space and will be kept much warmer and likely used less.
I’m thinking of using PGT Winguard Low-E vinyl windows/doors, but I’m open to other ideas there too. We have had good luck with the one install we did with PGT, but I can find plenty of horror stories. It also seems their sliders are not very waterproof which means they aren’t very energy efficient.
I had started to go down the path of electric tankless water heaters, but think I’m back to a hybrid in the garage with a recirc loop (researching recirc with Pex). The tankless power required and lower and lower flow faucets seem like a recipe for headaches.
This is my “forever” home, so trying to do it right and open to any advice you can give me. For the record, it will be very hard to talk me out of ICF as the house is close to the airport and I grew up going through hurricanes. I just don’t see anything better for strength/sound.
If I do any home automation, I think I will use systems that integrate with Google, rather than a centralized system that will be outdated in a couple years.
I’m not doing this to be zero energy or anything like that, but just trying to be efficient and do what makes sense. The rear roof points S/SW so would be ideal for solar, but not sure the returns are worth it yet. I know next year is the last tax credit though.
I’m sure there is more, but that’s a good start. Attached some rough sketches.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Hi 2008GT500,
My name is Steve. What's yours?
You could go with a flash and batt conditioned attic (https://www.greenbuildingadvisor.com/article/flash-and-batt-insulation). R-5 of closed cell foam might not be the greenest solution, but you could try to use an HFO-blown product.
Do you have cathedral ceilings anywhere? If so, be sure to read this article: https://www.greenbuildingadvisor.com/article/how-to-build-an-insulated-cathedral-ceiling
On the electric tankless water heater. That topic has been posted a few times on GBA. Each time the idea runs up against the realities of what you can do with a typical residential electrical service. The better option is a heat pump water heater (especially in your climate).
Hey Steve, my name is Tom. No cathedral ceilings, just a high traditional ceiling in the living area, but I'll take a look at that article.
I have to set an appointment with the utility company to discuss the loads of tankless, car chargers, etc, but I expect to be limited in my current capacity. I think the heat pump likely makes a lot of sense, I tried one in the old house and never had an issue with it.
The other thought that comes to mind is that diverting some of the efficiency funds to solar might be a better return on investment as solar efficiencies go up. I know a few articles I've read here have discussed that as a possibility and that was 5 years ago, so the returns should be even better today.
We've learned that the kind of insulation you use is less important than how air tight your house is! Make it tight, install a fresh air ventilation system and the best windows you can buy, and you'll have a great, comfortable house. I'd also go with minisplits, but tightness, ventilation and windows are the big three.
In reading about the polyiso on top of the roof deck, I find it intriguing, but it seems like it leaves a lot of opportunity for leakage around the trusses and tops of walls. The spray foam seems to be a much simpler way to seal the attic for a nice tight building and I will certainly look into the HFO Steve.
The other question my brother and I have debated is what to do with the soffit in a sealed house. If you leave the underside of the plywood exposed at the soffit, doesn't that present the opportunity for sorption, or not because that edge of the plywood is the same relative temperature? We were debating on vented vs unvented soffit, but the humidity in Florida will certainly get inside an unvented soffit unless you invest some serious resources.
Thanks Bob, I used a minisplit in my garage at the last house and am certainly considering them for a larger role in this house. It seems like the smaller minisplits are much more efficient and lose their advantage as you increase size. Do you have a brand preference? We installed a Mitsubishi at a clients house that seemed like a nice unit and have had mixed results with Carrier.
RE: Minisplit brands: I found a contractor who was, in 2011, a Mitsubishi "Diamond" dealer installing the units as supplement heating & cooling on vacation houses so I've stayed with them and the Mitsubishi brand with no regrets. And while I build in the Northeast, minisplits are great for AC and dehumidification, so expect they'd work as well there.
In Florida, you can put the water heater in the garage, so I see no downsides to a heat pump unit.
RE: Minisplit brands: I found a contractor who was, in 2011, a Mitsubishi "Diamond" dealer installing the units as supplement heating & cooling on vacation houses so I've stayed with them and the Mitsubishi brand with no regrets; great units and excellent factory service when you need it. And while I build in the Northeast, minisplits are great for AC and dehumidification, so expect they'd work as well there - less expensive heat, less expensive to buy and fewer issues. I fully expect to see minisplits take over the heating market in the next few years as they have in other countries.
In Florida, you can put the water heater in the garage, so I see no downsides to a heat pump unit.
Tom:
As Bob suggested, you need an air barrier strategy. This article should address most of your questions about what they means: https://www.greenbuildingadvisor.com/article/questions-and-answers-about-air-barriers.
Exterior rigid foam is another option. This approach can be made more economical by using reclaimed material.
On the split minis, Carl Seville is having issues with his Mitsubishi system. (See https://www.greenbuildingadvisor.com/question/ductless-mini-split-failures for more.) I have a Daikin ducted system serving my top floor and have had no issues (so far).