Hi gang!

I'm looking at building my first home here in the St. Louis area of Missouri. I'd like to make it as energy efficent and cost effective as I possibly can whilst retaining the everyday conviences of modern life.

I've been looking into a variety of technologies and building techniques to achieve my goals and keep it in a good price/performance area. Some of the things I'm considering are tankless water heaters, geothermal heating and cooling, southern exposure windows for passive solar heating, possible automated blinds to control temps in the summer, etc.


I have a ton of questions but figured I'd focus in on the major ones to get some ideas.


Geothermal Heating and Cooling

In Missouri is geothermal heating and cooling a practical solution, or would conventional high efficency setups be a better investment?



Radiant Heating

Can you install radiant heating floors in a house with a basement? Missouri is tornado territory and basements are almost mandatory here.



Solar Power

Is it worth installing a bank of photovoltaic cells here in Missouri or are we to overcast to take advantage of them?


These are my major questions and I welcome any input on the subject.

Thanks guys!

- Skip

You might want to build a storm shelter in your basement.  FEMA has plans that you can modify.  A storm shelter should include a reinforced concrete roof.

I had planned something along those lines with an insulated fireproof door. The room would double as a storage vault for valuable items.

If you do a geothermal system (not a bad idea in your climate, ashp's aren't as efficient when it gets really cold) you will want to get a desuperheater for your domestic hot water. Desuperheaters make the hot water costs almost free.

If I were building in that climate, I'd look at ICF construction from the basement to the roof. And go with a finished or conditioned attic.

Probably would have a minimum of R-20 walls, R-60 roof, R-10 under the slab, and minimal use of windows on the north side.

Can you install radiant heating floors in a house with a basement?

Yes. There is a product called Quad-deck that allows you to pour concrete floors over your basement so you can place hydronic heating tubes in the slabs for very efficient heating. However, you are probably looking for some air conditioning there as well and that is more difficult to do with radiant, forcing you to have more of a dual system.

Geothermal is nice, but your heating and cooling needs are not extreme enough to rule out an efficient air source heat pump either on the radiant side or via ductless minisplits.

Either way, be prepared to do a heat load analysis of your proposed new home which will be a good tool in determining the upfront costs and operating costs of different systems.

Geothermal is one of the few things you can get a tax break on with new construction. By the time you reduce the geo costs 30 %, you're probably not much higher than an air sourse heat pump. If you build with icf, you can eliminate the basement and just build a safe room.

Higher performance building envelopes tend to be more cost-effective than ground source heat pumps on new construction, but it takes a dedication to designing-in the performance from the get-go. Spending the money on the building envelope buys more in comfort & efficiency than radiant floors too.

Radiant floors are a cost adder, and don't add comfort to high-R homes the way they do to with homes of conventional R: Let's say you have a 2500' home with design heating load of ~15,000BTU/hr- that's 6BTU/foot of floor, which means the floors would be a cozy ~3F above room temp for the 1% of the time. At the average winter temps (or during most waking hours) the floor temp would be maybe a degree above room temp- hard to detect even in bare feet. Are you going to spend an extra 8-10 grand just to be able to have the extra cush when you get up at 5AM to pee on the coldest day of the year?

In a high-R house room-to-room temperature differences are small, and you don't really need a heat distribution system. In a very tight house (air tightness really is necessary to be able to get heat loads that low) you DO need active ventilation. When designed in conjunction with "point source heating", taking the bulk of the exhuast air from the rooms without the heating/cooling source(s) balances it even further.

It St. Louis the 99% heating design temps are in postive digits:

http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf

This means it's possible to heat & cool with high efficiency with variable-speed ductless air-source heat pumps ("mini-split", or "multi-split"). With an optimized floor plan and a tight high-R house you can usually heat and cool with one ductess-head per floor.

Designing the roof pitches to be able to mount PV panels is VERY MUCH a good idea. In some locations the subsidy for PV is high enough that payback is under 6 years, and with a high-performance building and heating with high-efficiency ductless a rack of PV and being judicious about the rest of your power use can turn even an R30-whole-wall building into a Net Zero Energy house. (Like Marc Rosenbaum does in MA : http://thrivingonlowcarbon.typepad.com/thriving-on-low-carbon/ )

Make ample use of energy use modeling before locking down the design. Optimizing the window glazing area & types can make a huge difference on heating & cooling loads. BeOpt is a DOE freebie that helps optimize different aspects of the construction for cost, and is good enough to be a crude passive-solar design tool. It's important to be able to figure out if adding another R10 on the walls is a better performance enhancement than reducing the U-factor of the windows from U0.30 to U0.25, etc. when parte your goal is to be cost-effective. See: http://beopt.nrel.gov/ (the BeOpt doesn't seem to be working this month) Underneath it all BeOpt is running DOE2 as the baseline energy use model, which IS downloadable this month: http://www.doe2.com/

A starting point for whole-assmebly (thermal bridging of framing factored in) R values can be found on table-2 , p10 of this document:

http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones

St. Louis is on the cool edge of zone 4, warm edge of zone 5, so you're looking at roughly R25-R30 for whole-wall R. With insulated concrete forms ~R22 is the basic model from most vendors, but the benefits of the thermal mass of the wall gives it performance roughly comparable to R25-R27 in a low-mass stick-built. And example of R25-R27 in a stick-build can be had with 2x6 construction using at least some advanced framing techniques (particularly at the corners), with cellulose or open cell foam in the caviites, and 2" of foil-faced rigid polyiso on the exterior, with a 3/4" air gap between the iso and the siding.

Building ICF basements and stick-built with exterior foam can work well, aligning the plane of the sheathing foam with the exterior EPS of the ICF. Putting 2" of Type-II EPS or 1.5" of XPS under the basement slab, butting the slab-foam with the interior EPS of the ICF (floating the slab) gives a nice thermal break at the footing too.

Whatever the construction type, defining the primary air barrier as a continuous layer from the sub-slab vapor barrier up and over the ceiling/roof and down again is important. Making every layer is air tight, but the layer(s) needing the most attention to detail at the interconnecting seams from floor to wall to window-flashing to ceiliin etc is the defined air-barrier. An air tight house is the cheapest efficiency enhancement that you can buy, but it doesn't happen by accident, or even as an afterthought. If you can get it tight enough to be less 1 full air exchanger per hour at 50 pascals pressure (also stated as ACH/50 a standard blower-door metric) you'll be in the 99th percentile of air-tighteness. Under IRC 2012 the tightness spec for production housing is 3ACH/50, which is tighter than when builders didn't care about air tigthness, but dead-easy to hit if you're paying any attention at all to every crack & seam, and it's not expensive. Experienced builders under Canada's R2000 program hit under 1ACH/50 often, even though they're only required to hit 1.5ACH/50 (half the leakage of an IRC2012 code-max.) While it's easier to hit those numbers with SIP or ICF construction, it's still quite do-able with stick built.

Skip,

Simple is Hard. Saving money and energy starts with a simple home design. Keep it simple to build and that savings can be put into the things that matter most. I'm an Architect and just finished building an energy efficient home for myself just outside Saint Louis for $100/sqft.

My house is as follows:
- R23 2x6 walls with blown insulation.
- R50 attic.
- White metal roof to minimize solar heat gain.
- Ground source heat pump (aka GEO) with horizontal loop field. Zoned for 1st and 2nd floor. We power down each floor when not in use.
- Energy efficient lighting everywhere.
- Energy star windows and doors. Home overhangs limit direct summer sun.
- Maintenance free exterior- metal siding and metal roof.
- Low flow water fixtures.
- Energy star appliances.

GEOthermal (really its called Ground Source Heat Pump when talking to mechanical contractors)
We used Water Furnace - 5 Series with horizontal loop field. I have a 2 story house so I included their Intellizone so each floor is zoned. Works fantastic and preheats domestic water as well. My home is all electric and the June power bill was $140.

Radiant Heat
Its a great system, but personally I think your money will be better spent on GEO and the exterior envelope.

Solar Power
Solar is great if you can do it. My main problem with solar is the cost and rate of return on the investment.

Best of luck...
Patrick

- R23 2x6 walls with blown insulation.

That's pretty good. How did you do that?

forgot to mention advanced framing to limit thermal bridging and rigid insulation exterior....

what is the conditioned space?

Posted By PWARNECKE on 12 Jul 2012 02:40 PM
forgot to mention advanced framing to limit thermal bridging and rigid insulation exterior....

To hit R23 for whole-wall with AF 2x6 takes about 2" of exterior EPS or 1.5" of iso.  If R23 is the center-cavity value it means you have about a 1/2-3/4" of rigid, and a whole-wall R of ~R17-R18. 

If the siding is attached by nailing through thin foam to the structural sheathing takes the whole-wall R a bit lower due to the thermal bridging of the multitude of nails, which have orders of magnitude more thermal conductivity than wood or foam.

But an air-tight R17 whole-wall is still a big improvement over standard construction of even 10 years ago, and outperforms current code min.

Posted By Dana1 on 18 Jun 2012 02:26 PM 

A starting point for whole-assmebly (thermal bridging of framing factored in) R values can be found on table-2 , p10 of this document:

http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones

This is a great place to really get information about building envelope design!

forgot to mention advanced framing

Was it the first advanced framing you did, or how did you get your crew trained to do it?