I am in the process of designing a house (+/- 4000 sq/ft) near Gainesville Florida. I have a 6.5 acres lot and would love to hear suggestions on how to design an energy efficient house for such climate. I am definitely sold on building ICF, low E windows, etc... I will have my own water well. I have a few questions : 1) what would be the R value recommended for walls and roofs ? 2) what type of heating/cooling system would do better ? is a heat pump recommended ? 3) solar panels ? 4) are there any geothermal system that could use the water temperature in the well ? if yes, how much do they usually cost ? Any input is very well appreciated. Thanks

See table 2, p10 of this document  as a starting place for R-values.  Gainesville FL is in US climate zone 2, so use the second row. Also note, those are "whole assembly" values, that factors in the thermal bridging of rafters/joists/studs etc- the center-span R is higher than that.

Controlling solar gain is more about R-value though, and solar gain is your primary concern.  Shading factors such as roof overhangs, and minimizing or even eliminating west facing windows (where the sun is low, and over hangs can't shade them) are key.

CRRC rated "cool roof" or mass roof materials such as tiles make a huge difference in peak & average roof temps, making roof-R more effective. 

An ICF or SCIP roof is a more valuable place to put the thermal mass than the walls from a load-reduction point of view, and is more hurricane-proof than stick-built roof structures.

Heat pumps yes, geothermal maybe, but not necessarily.  Setting up the roof angles and siting for photovoltaic panels is a good idea on any new construction, and depending on the relative subsidies, PV + ductless air source heat pumps can sometimes be a better utilization of funds.  If you're on the gas-grid it might be cheaper to heat with gas, but the cost of the additional system may not have payback over high-efficiency heat pumps.

Heat pump hybrid hot water heaters located inside of conditioned space (but not where you have to listen to them) make a lot of sense in that climate too.

The cheapest efficiency improvements are with the mechanical systems- they're best when cooked into the design, which has every thing to do with site factors and solar orientation, over hangs, etc.  A decent freebie download to help optimize it is BeOpt, only recently released for public consumption after a decade or more of development at the US DOE.   A correctly designed overhang pays back a lot more in load reduction than a photovoltaic array costing 10x as much.

If your well water is of a quality to support GT-
and if you have a couple Gallons per minute above peak GT required flow (for general use of assuming 4 ) - guessing 9 or 10 total peak GPM;
and if the lift of the water at a given pressure of about 45 psi for some usual use- is less than about 110 ft in a "dynamic" useage for the GT,
-generally- (GT highest efficiency systems can only need 30 psi that wells run at with household 240-watt booster pumps for house pressure when needed)

once you know these things for a start for GT open well usage, then that would be a good starting consideration. Some local installers and manufacturers right around Fla would also know "HOW" if you need to test a flow at a particular dynamic -.

Other methods of adding split- but non-Hot-Water producing heat pumps for a larger cooling requirement could use both technologies of a split air heat pump WITH a small (30,000) GT system , having the split do more additional cooling as a backup to the GT Cooling when (if) the GT unit as a system was not making HW while then called in a Cooling cycle. There are Air and GT Ht Pumps that can make HW for you.
A credit to the ENTIRE GT system and as related contract with "other" Gt-connections, may end up as mostly a GT System of things that are allowable in a TAX credit: Check with your local GT installers and AND your CPA. Ht Pumps making HW can do a little more or a lot more with any thoughts and plans for POOL heating and Pool Cooling and radiant HW in under a once-in-a-while cold tile bathroom floor or somethings like that.

If your local city/county will be adopting the 2012 IRC, you will need the following to be code compliant:

- Minimum of R-49 in the attic
- Minimum of R-20 in the walls
- Must past a blower door test
- Windows must have a U-Value of 0.30 or lower

there are other factors but these are the main ones I have read about...

I've spent time near the equator in tropical climates and there you really want large overhangs and windows on the north & south sides. Cooler and better for keeping the walls dry. It's so hot that just the radiant heat from the ground is unbearable if you want to sit outside under the overhang (ie, veranda/porch). An additional short wall at the edge of the overhang (like a railing but may be at ground level) helps with this. And of course trees for shade really help.

Posted By knotET on 08 May 2012 08:44 PM
If your well water is of a quality to support GT-
and if you have a couple Gallons per minute above peak GT required flow (for general use of assuming 4 ) - guessing 9 or 10 total peak GPM;
and if the lift of the water at a given pressure of about 45 psi for some usual use- is less than about 110 ft in a "dynamic" useage for the GT,
-generally- (GT highest efficiency systems can only need 30 psi that wells run at with household 240-watt booster pumps for house pressure when needed)

once you know these things for a start for GT open well usage, then that would be a good starting consideration. Some local installers and manufacturers right around Fla would also know "HOW" if you need to test a flow at a particular dynamic -.

Other methods of adding split- but non-Hot-Water producing heat pumps for a larger cooling requirement could use both technologies of a split air heat pump WITH a small (30,000) GT system , having the split do more additional cooling as a backup to the GT Cooling when (if) the GT unit as a system was not making HW while then called in a Cooling cycle. There are Air and GT Ht Pumps that can make HW for you.
A credit to the ENTIRE GT system and as related contract with "other" Gt-connections, may end up as mostly a GT System of things that are allowable in a TAX credit: Check with your local GT installers and AND your CPA. Ht Pumps making HW can do a little more or a lot more with any thoughts and plans for POOL heating and Pool Cooling and radiant HW in under a once-in-a-while cold tile bathroom floor or somethings like that.

Do you have any rough estimate for such system ? Am I not better off having a normal cooling system and put solar panels instead ? Thanks

Posted By Lbear on 09 May 2012 01:37 AM
If your local city/county will be adopting the 2012 IRC, you will need the following to be code compliant:

- Minimum of R-49 in the attic
- Minimum of R-20 in the walls
- Must past a blower door test
- Windows must have a U-Value of 0.30 or lower

there are other factors but these are the main ones I have read about...

Thanks for your reply. I am looking to build the max efficient as I can for the location (Florida). What would be the max R value for walls and roof before it is just a waste of money to increase that value ?

Posted By Dana1 on 08 May 2012 06:43 PM
See table 2, p10 of this document  as a starting place for R-values.  Gainesville FL is in US climate zone 2, so use the second row. Also note, those are "whole assembly" values, that factors in the thermal bridging of rafters/joists/studs etc- the center-span R is higher than that.

Controlling solar gain is more about R-value though, and solar gain is your primary concern.  Shading factors such as roof overhangs, and minimizing or even eliminating west facing windows (where the sun is low, and over hangs can't shade them) are key.

CRRC rated "cool roof" or mass roof materials such as tiles make a huge difference in peak & average roof temps, making roof-R more effective. 

An ICF or SCIP roof is a more valuable place to put the thermal mass than the walls from a load-reduction point of view, and is more hurricane-proof than stick-built roof structures.

Heat pumps yes, geothermal maybe, but not necessarily.  Setting up the roof angles and siting for photovoltaic panels is a good idea on any new construction, and depending on the relative subsidies, PV + ductless air source heat pumps can sometimes be a better utilization of funds.  If you're on the gas-grid it might be cheaper to heat with gas, but the cost of the additional system may not have payback over high-efficiency heat pumps.

Heat pump hybrid hot water heaters located inside of conditioned space (but not where you have to listen to them) make a lot of sense in that climate too.

The cheapest efficiency improvements are with the mechanical systems- they're best when cooked into the design, which has every thing to do with site factors and solar orientation, over hangs, etc.  A decent freebie download to help optimize it is BeOpt, only recently released for public consumption after a decade or more of development at the US DOE.   A correctly designed overhang pays back a lot more in load reduction than a photovoltaic array costing 10x as much.

Would you recommend a roof with ICF or a standard roof with the spray foam ? Hurricane not really a factor in that area, and the local electrical company offers incentive for the foam solution. Is the ICF much more efficient ? Thanks.

Posted By serhito on 09 May 2012 11:25 AM

Posted By Lbear on 09 May 2012 01:37 AM
If your local city/county will be adopting the 2012 IRC, you will need the following to be code compliant:

- Minimum of R-49 in the attic
- Minimum of R-20 in the walls
- Must past a blower door test
- Windows must have a U-Value of 0.30 or lower

there are other factors but these are the main ones I have read about...

Thanks for your reply. I am looking to build the max efficient as I can for the location (Florida). What would be the max R value for walls and roof before it is just a waste of money to increase that value ?

Those R values are for a much colder climate than Gainesville, and not at all appropriate for a Gainesville climate.

IRC code min for US climate zone 2 is:

Ceiling R-value	30
Wood Frame Wall R-value	13
Mass Wall R-value	4/6
Floor R-value	13
Basement Wall R-value	0
Slab R-value , Depth	0
Crawlspace Wall R-value	0
Fenestration U-Factor	0.65j
Skylight U-Factor	0.75
Glazed fenestration SHGC	0.30

The max values depends a lot on how that R is achieved- R30 in closed cell foam is $5 per square foot,  with EPS it's $3/ft. but with cellulose its $1/ft.

For a rational starting point look at Table 2 p10 of this document:

http://www.buildingscience.com/docu...mate-zones

The second row is for climate zone 2, which includes Gainesville.

Prescriptive R/U values aren't the most effective way to get to highest performance. Using energy modeling tools like BeOpt or Hot2000 do a much better job. It's very easy to hit particular R and U values and still end up with an energy pig compared to the performance that could be achieved with the design simulated and tweaked for orientation and site factors.

In Sweden codes have shifted toward performance-by-design rather then prescriptive-R and it includes post-construction post-occupation verification, with PENALTIES. That puts a significant burden on the architects and engineers as well as the construction contractors to really get it right rather than going with a "it meets code-min for R & U", attitude.

I just got off the phone with Air-Force base IQ GeoThermal and they were excited about the 45-50% savings over a WF Versatec (?sp) single speed..... 4:ton WF to a 4ton IQ. I can see why the V Star Bristol compressors were tested about 5 years - for the "get it right" group.
SER
a cost is then about that of a First cost and the 4-to-7 year ROI usually comparing if you want all exact zones covered by Mini-Split Variables or a multi staging a/c or ht pump as follows: Do you qualify for credits? Do you want a couple of space heaters and Hi Efficiency like that of the very latest Air Ht-Pumps (AHSP as to GSHP) or just very efficient a/c?

Mini ASHP + a HW heater with an a/c dehumidifier behind walls for quietness but needing open space will also be to 'rob' heat from what is  called "recovery" from an area (there are now several brands HtP or other names x HW heating)
OPTIONS:
if going  to ducted distribution:
What about zoning in 3 or 4 areas then to be considered and IF GSHP back to credits (ask your advisor cpa)
and what if SOLAR? Will you have 100% for all HW with a Mini-Split HtPump and a SMALL hi-efficiency a/c?
Enjoy Fla several ways about all that comfort-ability.

Others in other threads have a few more "regular a/c" ideas that are relatively about your greener concerns for a lot of Cool-ness

Posted By serhito on 09 May 2012 11:25 AM


Thanks for your reply. I am looking to build the max efficient as I can for the location (Florida). What would be the max R value for walls and roof before it is just a waste of money to increase that value ?

Be careful with the roof overhang, even though you are not in a hurricane zone, you will still get 100MPH+ winds. A large overhang acts like a sail and wants to lift itself off of the home. Check your code but I believe 18" - 24" is the MAX overhang allowed. You don't want your roof peeling off in high winds.

The most inexpensive method will be wood truss with blow in cellulose. The strongest & most expensive roof would be ICF/concrete. The better option would be steel roof SIPs.

Check your code but I believe 18" - 24" is the MAX overhang allowed.

I don't think code limits your overhang. It is determined by the structural engineer. I have overhangs of 3'-4'. In addition to hurricane ties, number and type of fastener, together with roofing materials can be manipulated to get uplift resistance.

done

Posted By ICFHybrid on 11 May 2012 12:18 AM

Check your code but I believe 18" - 24" is the MAX overhang allowed.

I don't think code limits your overhang. It is determined by the structural engineer. I have overhangs of 3'-4'. In addition to hurricane ties, number and type of fastener, together with roofing materials can be manipulated to get uplift resistance.

According to this study, the largest roof overhang permissible with a SIP roof is 2 feet. Longer lengths theoretically "can" be done but it is not recommended. There is a lengthy study on this topic but in essence the longer the overhang, the more it acts like a sail in the wind, trying to pull the entire roof structure up and off of the homes walls and basically "fly away".

Think of an airplane and the longer the wingspan, the greater the uplift force it has on the plane. Ideally you don't want your roof lifting up like a 747.

SIP ROOF ENGINEERING STUDY

That study describes a prescriptive method for SIPS. It doesn't say anything about the full range of SIP capabilities or other construction methods. Roof overhangs larger than 24" are quite acceptable.

If you look carefully at a wide range of common framing connectors you will see that most have specs for uplift forces. They are employed to hold down walls and roofs.

Roof overhangs larger than 24" are quite acceptable

And useful. There are lots of options to make it strong. A veranda is just a very large overhang.