Hi everyone! I've lurked this forum in the past on many DIY projects on our current home. For this I felt I needed to join! I'm going to read everything I can on the subject, but in the spring we're going to start construction on a new home. We already have the land purchased. It will be approximately a 2000 sq ft house with a full basement. 50% of the basement walls will be framed due to a sloping landscape offering a walkout. My wife and I both dislike forced air heating and we've heard a lot about radiant floor heating. I've looked into a product called warmboard which looks promising. I've also heard conflicting reports on using radiant as a sole source of heating and that a backup furnace is needed. If that's the case, I don't know if it make sense. Also, what do people do for cooling that are using radiant for heat? It's obvious I'm a newbie to this stuff, but to be honest, we've interviewed several contractors in this area and many/most do are not interested in building a "non standard" home. In our area, contractors are very simple and like to do things they way they have always done them. Having said that, I wouldn't want a builder to "practice" on us anyway. I honestly don't think there is a builder in this area that has experience with this type of alternative HVAC. Having said that - do you all have any recommendations for things that must be done or questions we can ask to build an energy efficient home within reason? As of now I know we are going with 2x6 exterior walls with either spray foam insulation or the "blown in" insulation (not sure what they call that). Thanks for any advice!

You may use a backup fuel source but not a heat source. We have designed many "radiant only" homes over the years.

We use Warmboard on many new projects as it is tough to beat a floor deck with radiant in one.

If you find the right builder it can be done, if you can't there are other options such as Gypcrete and others.

Cooling is best done with a ducted mini-split.

Foam board under siding and batts in the walls with cellulose or glass in the attic.

I'll dive in. It makes sense to build a better house! But if you simply cannot (where are you and what is your climate zone?), at least make it TIGHT!!!. Most of your standard contractors know nothing about how to do this, so you'll have to learn and insist that they build it right. Line up a local blower door guy/energy auditor and have him test the house BEFORE you insulate. It should be very tight by then, otherwise all the other advice you'll get is meaningless. Your builder might say that the insulation will tighten the house. Ignore him; he's wrong. A good goal is 1 ACH50 which is actually achievable, although not necessarily easy with standard practice. 3 ACH50 is the highest you should accept. Note that with a leaky house, the insulation doesn't matter so much since most of your heat will be lost through air leaks anyway.

Awesome, this is the kind of info I wanted and thank you both very much.

We're in Zone 5, not too far from 6. Our zip code is 52726, we basically live on the boarder of Iowa and Illinois near the Mississippi river right in the middle of the east boarder of Iowa.

Also I should have added-

If we do radiant floor, should we also do geothermal?
Can we do radiant floor in the basement floor and garage floors as well?
If I have a large detached shop (Will have it at some point, I don't know if we'll build it at the same time as the house or not) how should I heat that?

Near Petosi.

Bob is right. Start with a tight house but don't forget to install an ERV. We use Renewaire built in Madison. A 90 will do fine.

Geothermal will be a long payback on such a modest house.

Radiate the shop. See your options at GararageJournal...

Modest house, 2000 sq ft ranch? We tried to design it even smaller and think this is too big. Haha.

And by shop, I mean probably a 30x40 garage/shop.

We just finished a 5000 sq.ft. west wall all glass, radiant all three floors.

Poor guy doesn't have a shop though. Mine is 40x60 all radiant with twin head heat pump for cooling and heat if I let it.

Now that's a big house.

I like the sounds of your shop.

I guess the biggest question is how do I find a competent HVAC contractor in the area that will do radiant properly? I've had little to no luck so far.

We find can help if you send a plan. The further out in the country you go the harder it is.

Email it to you?

Just poured footings for a similar house(2000SF, full W.O. basement , ICF) . We originally specced radiant in the basement slab, but upon further thought, I am not going to do that. I will still insulate under the slab, but no pex. The main reason is that I won't be spending that much time down there. It will never be a habitable space, just storage, single bay garage and pistol range The slab radiant would be great for a regularly occupied space, but I don't want to be dumping heat into a slab/space when I am not there, and the response time of a slab makes this seem not so practical for that area. With insulation, I can space heat when needed for comfort where/when I am down there.

The main floor will be warmboard radiant over open web trusses. No need for a backup heat system with radiant. This sounds like someone trying to sell you something. Ask the person who said that if a furnace system needs a backup furnace system... If they say no, then ask them why radiant would be any different(people have been heating with soul source radiant since domestic heat was first dreamed up). Both a furnace and radiant need electrical power to function, but if you have a gas fired heatsource, you can run a radiant system on a surprisingly small generator... The cool thing about heating with hot water is that there are a lot of ways to make that. It opens the door for fairly easilly incorporating solar heat, or even a wood fired boiler at some point in the future.

If you need cooling, I would look at incorporating it with a HRV/ERV ventilation system, or one or two small area AC's who's output would be distributed by a HRV system. I have a small split A/C unit in storage, that I left room in the plans to install if I feel the need, but my climate rarely warrants the need for it...

Good luck on your project.

www.BadgerRadiantDesigns.com

If you are DIY oriented like you indicated, there is a considerable amount of information on our website about DIY hydronic radiant heating including a suite of free design software. There is also guidance on how to select a good HVAC company too. You might start by reading the associated instructions for our hydronic radiant floor heating design software:

Borst Hydronic Radiant Floor Heating Design Software

BTW, we believe a ranch style home is the most energy efficient conventional style of home that can be built. Keeping the size down to the minimum square footage needed and minimizing the window area (especially on the east, west and north walls) is also the best starting point.

In case you missed it, BadgerBoiler mentioned rigid foam under the siding. Stick framing suffers a lot of heat loss through thermal transfer from all of the framing- often 25%. A layer of foam on the outside serves as a thermal break so that you actually get close to the 'advertised' R-factor in your walls. As was said, build a good envelope, and you will save by requiring a smaller HVAC system, and of course in monthly utility bills.

We are building at the moment and have gone through all these questions. Consider 2x4 framing instead of 2x6 and use exterior foam as mentioned above. I am going with ThermalStar LCI-SS. Do you have access to nat gas? If not consider geo with propane backup. With the 30% govt tax credit the cost of the geo system is worth considering if your options are propane or electric. Don't overlook the air sealing as also mentioned above. Really no rocket science here but you need a good plan and someone to execute it, which can be you if you feel up to it.

Posted By sailawayrb on 06 Dec 2015 09:27 PM
If you are DIY oriented like you indicated, there is a considerable amount of information on our website about DIY hydronic radiant heating including a suite of free design software. There is also guidance on how to select a good HVAC company too. You might start by reading the associated instructions for our hydronic radiant floor heating design software:

Borst Hydronic Radiant Floor Heating Design Software

BTW, we believe a ranch style home is the most energy efficient conventional style of home that can be built. Keeping the size down to the minimum square footage needed and minimizing the window area (especially on the east, west and north walls) is also the best starting point.

Thank you, I'll certainly be reading up on your website!

Posted By thescottcav on 07 Dec 2015 09:06 PM
We are building at the moment and have gone through all these questions. Consider 2x4 framing instead of 2x6 and use exterior foam as mentioned above. I am going with ThermalStar LCI-SS. Do you have access to nat gas? If not consider geo with propane backup. With the 30% govt tax credit the cost of the geo system is worth considering if your options are propane or electric. Don't overlook the air sealing as also mentioned above. Really no rocket science here but you need a good plan and someone to execute it, which can be you if you feel up to it.

Why not 2x6 with the exterior foam? We do have natural gas so no propane necessary.

Posted By rgonyer on 08 Dec 2015 06:59 AM

Posted By thescottcav on 07 Dec 2015 09:06 PM
We are building at the moment and have gone through all these questions. Consider 2x4 framing instead of 2x6 and use exterior foam as mentioned above. I am going with ThermalStar LCI-SS. Do you have access to nat gas? If not consider geo with propane backup. With the 30% govt tax credit the cost of the geo system is worth considering if your options are propane or electric. Don't overlook the air sealing as also mentioned above. Really no rocket science here but you need a good plan and someone to execute it, which can be you if you feel up to it.

Why not 2x6 with the exterior foam? We do have natural gas so no propane necessary.

IRC 2012& 2015 code minimum for US zone 5 is 2x6/R20, or 2x4/R13 + R10 continuous insulation. If you do the 2x4 wall you have comparable overall thermal performance, but since the wood sheathing is stubstantially inside the thermal boundary there is effectively zero risk of developing mold/rot conditions even without using interior vapor retarders (other than standard latex paint). This gives the assembly much higher drying capacity than a 2x6 wall, which would either need to be built with a rainscreen (back ventilated siding) or a Class-II or Class-I vapor retarder on the interior side.

If you built with 2x6 framing + exterior foam you would need an absolute minimum of R7.5 on the exterior to be be able to leave the interior side vapor open. The minimum exterior foam requirements for adequate dew point control without interior vapor retarders is prescribed in the IRC:



http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_7_sec002_par025.htm

Code minimums are prescribed in chapter 11:



http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_11_sec002.htm

Mind you, a definition of code minimum is "The lousiest performing house that is legal to build." It's not necessarily the most financially rational, or the most comfortable, just legal.

Thinking over the long term, it's usually rational to build the thermal performance to a level where the energy needs of the house could be met with a photovoltaic (PV) solar array that fits on the roof. While PV used to be one of the most expensive energy sources, it's widely anticipated that within 15 years it will become one of the cheapest sources of energy. The approximate whole-wall-R values at which fitting sufficient PV on the roof to cover it all can be found in Table 2 of BA-1005, a piece of analyisis performed by the Building Science Corp a handful of years ago. In time since it was written the installed cost of rooftop PV has dropped by more than half and the average efficiency has crept up, which means it now takes slightly less roof area, but it's still a reasonable estimate. See:



http://buildingscience.com/documents/bareports/ba-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones/view

Note, the prescribed R30 wall for zone 5 isn't R30 center cavity, but rather with all thermal briding factored in. An example stackup of a wall meeting that performance level would be a standard 2x6/R20 wall with 2.5" to 3" of exterior rigid polyisocyanurate foam sheathing, or 3.5"-4" of EPS. That's fairly straightforward to build, but the average tract home builder and many custom builders don't necessarily have the experience or skilled crews to pull it off. Still this type of construction is becoming more common every day in colder climates, now that code minimums for zones 6 & 7 pretty much require insulating sheathing to get there.