Lets start with the first idea - that you have to condition the attic.

You can of course put the unit(s) in a closet and run the ducts just above the ceiling plane. Then you insulate right above that.

Flood zone does not preclude putting ducts below the house. We have a house on a barrier island that is in VE zone. You have to build above the BFE so the ducts should be fine - if not you have a lot more to worry about. That house has first floor ducts below the house.

Ok - so if none of that works. 2018 IECC specifically talks about burying ducts in insulation which is an option. Don't want that - rigid foam on roof decks are great but don't expect to find anyone who wants to do it. It just isn't done and reaching out of the norm is not easy. Most will spray foam at way under R-38 and call it a day. It isn't a terrible idea but I couldn't bring myself to do it. I buried the ducts on latest build and did an attic conditioned closet. I did a slab and it is a 2 story. Heresy.

What is your goal? Lowest energy costs? Sometimes solar gets cheap enough that fighting the battle just isn't worth it. I am doing a 13kw system which will more than cover my HVAC and house needs. The house is pretty cool now with the drywall up and no a/c yet.

David - appreciate the response. Goals are efficient house, lower bills. House we tore down was 1960...not efficient at all. Trying to do better without being silly or breaking the bank. Building this with insurance money and savings and sweat.

Lets start with the first idea - that you have to condition the attic.

You can of course put the unit(s) in a closet and run the ducts just above the ceiling plane. Then you insulate right above that.

I wish we had a spot for the A/C in the living space, but we don't. even so, definitely not ducting.

Flood zone does not preclude putting ducts below the house. We have a house on a barrier island that is in VE zone. You have to build above the BFE so the ducts should be fine - if not you have a lot more to worry about. That house has first floor ducts below the house.

I will look into this. I have never seen it don't like this. maybe a regional thing? would that require floor vents??

rigid foam on roof decks are great but don't expect to find anyone who wants to do it.

this is definitely a concern. We are contracting this out ourselves and might have a little sway.

I buried the ducts on latest build and did an attic conditioned closet. I did a slab and it is a 2 story. Heresy.

we do have a loft space with knee walls...we have considered bumping part of this out as a 'mechanicals' room. This would be my last choice though.

Sometimes solar gets cheap enough that fighting the battle just isn't worth it. I am doing a 13kw system which will more than cover my HVAC and house needs. The house is pretty cool now with the drywall up and no a/c yet.

Last i checked, the payoff for solar was 14 years or so. I should peek at this again. but right now I can't add another thing to research!!

What you are trying to do needs to be integrated into the design of the house, not treated as an add on.

Have you considered ducted split systems?

I agree with David's points. These decisions are design dependent yet it sounds as if design is finalized. Some of the best advice on this forum is to use architects experienced in your goals. I think it's wise to similarly involve a builder early, even if it's only in a consulting role.

'Knee walls' is something that ties right into the conversation as finished spaces in attics are seldom airsealed and insulated properly with conventional construction.

Have you considered getting Energy Star certification or tried reaching out to energy raters in your region?

We are building in the south (Birmingham area) and will be doing open cell foam 8-9" on the rafters with a radiant barrier above. Builder preferred open to closed for cost as well as "you want to know when you have a leak". This will get the attic to be semi-conditioned space where the air handler and ducts will be. We meet with the HVAC folks and will ask if the ducts are still insulated, etc.

Roof will be composition shingle (metal wasn't in the budget and was to $$$ to insure).

Are you sure about that? I'm also in zone 2 (and also a flood zone) and it actually was cheaper having a metal roof in terms of insurance purposes. Also while a standing seam metal roof is much more expensive, a 5 v crimp roof isn't that much more overall and will keep the house cooler and last a heck of a lot longer.

These decisions are design dependent yet it sounds as if design is finalized. Some of the best advice on this forum is to use architects experienced in your goals. I think it's wise to similarly involve a builder early, even if it's only in a consulting role.

Well Springtime I involved my builder from day 1. In fact he sold us the lot. And while in the design phase, I asked numerous times about having the HVAC guys design a system based on the calcs. I was told not to "worry". Now my whole AC system has to be redone and we've only been in the house since end of April.

So sometimes even doing the right thing doesn't work, especially when dealing with the good ole boy network.

OP if you are in SW Florida message me and I'll give you the name of the company who came in after the fact and did our blower door test, as well as figured out what was wrong. They are considered the best in the area for doing HVAC calculations.

What is your foundation and where are you in construction? In our VE zone, we are 10 feet up on pilings. The ducts are under the house and the unit hangs below. It isn't fantastic but since the house is not occupied in the winter, the primary concern was a/c and keeping ducts out of the roof for low cost.

My problem with ductless has to do with bedrooms and also aesthetics. They require somewhat of a sacrifice - but they are the best. Quite the resale risk in my market and price point. And a head in each bedroom winds up being significantly oversized. And not having a head requires an open door which is not acceptable to me.

Sam - your plan doesn't compute. Foam on the rafters makes a radiant barrier not functional. You have to have an air layer to have an effective radiant barrier. Generally, when you foam the rafters, the attic is conditioned. Not semi. So the problem is that you have a larger conditioned area. Then the foam is usually done pretty thin and not even at code levels. So you have a huge area of less than code insulation.

Springtime -

Some of the best advice on this forum is to use architects experienced in your goals. I think it's wise to similarly involve a builder early, even if it's only in a consulting role.

I have a call into my architect to get her opinion. I have spoken to several 'builders; and they do bats in the ceiling, some do open cell on rafters, most do less than code. I have one other call to make (friend of a friend who has built 4 houses). Hopefully he can offer some insight as well. Harvey recovery is still going strong...it is difficult to get anyone to quote actual work, much less get people to consult on future work. 5/6 requests for quotes go unamswered. These are reputable people, not just fly by nights.

Have you considered getting Energy Star certification or tried reaching out to energy raters in your region?

I looked briefly. If I recall, the program is only available to builders, not individuals.

Are you sure about that? I'm also in zone 2 (and also a flood zone) and it actually was cheaper having a metal roof in terms of insurance purposes.

I checked with my insurance twice and also had a friend run the numbers through her company (Allstate I believe). The insurance was higher because the value of the home was increased.

Also while a standing seam metal roof is much more expensive, a 5 v crimp roof isn't that much more overall and will keep the house cooler and last a heck of a lot longer.

My husband vetoed the 5v crimp because of the exposed fasteners and the reliance on rubber washers in our hot climate. He doesn't want to have to climb around and inspect and worry about failures.

I was told not to "worry". Now my whole AC system has to be redone and we've only been in the house since end of April.

So sometimes even doing the right thing doesn't work, especially when dealing with the good ole boy network.

We have been trying to nail down mechanicals since we decided on and purchased this plan. I have been told 'don't worry' we can work with this by several reputable local HVAC folks. It is really hard to get systems designed around here based on plans. My husband is actually a mechanical engineer who briefly worked commercial HVAC after grad school. He is running a manual j and will be following the HVAC decisions closely. I have a feeling, we will not get this nailed down until the framing is done. Not ideal for sure, but I'm getting no specifics based on plans alone.

OP if you are in SW Florida message me and I'll give you the name of the company who came in after the fact and did our blower door test, as well as figured out what was wrong. They are considered the best in the area for doing HVAC calculations.

Appreciate the offer, but I am south of Houston, TX.

David -

What is your foundation and where are you in construction? In our VE zone, we are 10 feet up on pilings.

We are doing concrete piers, finished floor will be approx 4.5 feet above ground. Crawlspace will be mostly open. Will use landscaping and maybe a little open skirting around the back porch and stairs.

My problem with ductless has to do with bedrooms and also aesthetics.

I do appreciate the efficiency of ductless, but I don't want them in every room. ugly.

@David Cary - Thanks for jogging my memory, I don't think we will have a radiant barrier after we decided to go with foam. Since the roof is going on this week, always a good time to check in with the super to confirm.

I found this as an amendment for Alabama. Does this make sense?

R402.2.2.1 (N1102.2.2.1) Semi-conditioned attics.

Where table N1102.1.1 (R402.1.1) requires R-30 or Table

N1102.1.3 (R402.1.3) requires a U-factor of 0.035, Sprayed

Polyurethane Foam (SPF) with a U-factor of 0.05 or R-value

of R-20 shall be deemed equivalent to the provisions in

N1102.2.2 (R402.2.2)

Table 402.1.2 from IECC 2015 to current is best prescriptive guideline for cost effective energy efficiency. I doubt using weaker local amendments is good strategy. Some energy efficiency experts feel that R49 is good minimum for ceilings in ALL climates and would agree, if the ceiling is traditional vented attic where thick layers of insulation are easy to apply and affordable (loose fill). Some high performance projects in cold climates approach R100 for ceiling.

These are international code minimum prescriptive numbers and it's easy to use other compliance paths to demonstrate equal total performance through other balancing improvements. Renovations of vaulted ceilings and insulative sheathing above the roof deck can make sense to go with weaker values. Spray foam applied to bottom of roof decks usually have substantial thermal bridging through rafters or truss chords, often more than the vented attics that prescriptions are based on so I don't think they deserve much leeway. Martin Holladay has the classic article on this common code violation.

Efficient homes heating with mini-splits don't need heads in every room, but will need their doors open during hot or cold weather, a deal breaker for many. Then there is David's point about resale but I think good implementation could help tamp down this possible sentiment. Haven't built ductless yet but open to it if owners are. The efficiency one gets with Mitsubishi's smallest unit is unbelievable. One head replaced a whole house furnace in my personal small home, granted winter design temps are stretching it.

Energy Star is for all homes. Homeowners or owner builders are eligible but may have a steeper learning curve to get the right details. Always involve a rater early, preferably with feedback during the design stage.

Cpartist, sorry for your trouble. With everything you have had to put up with, it's not surprising they flubbed an important technical detail of your build. I think people who value efficiency have to do extra research to ensure they are getting the right feedback on their design and selections. The architect or builder should have the right knowledge and experience in your goals and I think the best projects are collaborative from the beginning.

Most build teams valuing efficiency still include HERS raters (Energy Star) and mechanical engineers specializing in HVAC for services like Manual J, D, and S. Third party diagnostics, commissioning, and verification usually help ensure a good investment in home performance certifications like Energy Star.

DOE's Building America Program documents best practices for various climate zones. Here's link to information about applying spray foam under roof decking in your climate zone:

https://basc.pnnl.gov/resource-guides/application-spray-foam-insulation-under-plywood-and-osb-roof-sheathing#quicktabs-guides=1

I recommend you get a local HERS rater or residential energy consultant involved sooner rather than later. They can help you make an informed decision about the best way to achieve your objectives. They can also recommend appropriate third parties e.g., residential HVAC designers (with all due respect for your husband's engineering abilities, if design of residential HVAC systems isn't his day job, you will be well served getting technical help and advice from folks who do it for a living. It also won't likely be an architect.)

I recommend you focus on what is important to you and eschew the various energy efficiency pedigrees like Energy Star.

I agree having engineering, design, or building background would still benefit from hiring a rater or residential HVAC designer. For those researching energy efficiency and interested in better performing homes, be weary of builders or architects suggesting Energy Star isn't worth the investment.

Going high performance, like passive house probably makes sense to skip a lesser performing standard like Energy Star. I also understand why some choose not to participate in regional performance standards, like EarthCraft or GreenBuilt in our region. Most regional programs use Energy Star as the baseline, as it's the most affordable and effective standard to ensure quality.

Energy Star is not just an energy efficiency certification. It's an extensive third party verification system that results in better performing homes. In simple terms, the program makes sure that homes meet minimum building codes that include life-safety concerns. Even for builder's like us, that use Energy Star on every home, having someone check and verify is invaluable.

On a recent build, the rater discovered the HRV ducts were installed in a manner that made the outdoor air ventilation system useless. It was an easy fix and I wonder how long it might have been before we noticed the problem. Hiring HERS raters or HVAC system designers for upfront design goals is only the first step.

Most builders don't own fan flow meters for checking bath/kitchen vents, duct blasters for duct installation quality and blower doors for measuring airtightness; the most important metric in home performance. The rare builders that do use this equipment, know the rater double checking their work is a good thing.

Some builders or architects probably have bad experiences with the program which could be the result of a crappy rater or other non-conforming team member. Usually it's because they have a hard time meeting the minimum international building codes that the Energy Star program is enforcing. Some builders and architects want to use the bare minimum amount of HERS raters services to use alternative compliance paths for skirting code minimum prescriptions. Along with hiring the right build team, Energy Star is among the best possible investments for a better built home.

Our company became an Energy Star back in 2000 and produced a number of Energy Star and other energy "pedigree" homes. While some appreciated the enhanced comfort and energy efficiency, we found no consumer demand in our market for the pedigrees.

A problem with Energy Star and other pedigree programs is the assumption that what is appropriate or cost-effective on average is such for all consumers (in a given state or climate zone.) In the real world, consumer's discount rates, investment lifetimes, energy prices, and the purchase price of components and systems vary. Consumers who want a high-performing home and who can live without the pedigree on the wall are free to invest in only those improvements which make economic or environmental sense to them. To this end, we find DOE's Building America Program a more useful one.

Consumers who want a pedigree for their home would be well served to investigate a variety of alternatives and not tacitly assume Energy Star is the best for them.

Pedigree on the wall is distracting language to what Energy Star and Building America represent. As far as I know, there is no Building America Program that offers third party quality certification for homes other than Energy Star as listed on this Building America Solutions page. I believe the other few programs listed there use Energy Star as a prerequisite. There are few options that will result in better construction of "comfortable, healthy, durable, and energy efficient homes."