Hi folks.

I'm at the point of looking for a new home.  One question is whether that's  the purchase of an existing home or buy some land and put up my own custom.

What I'm having a hard time wrapping my head around is ballpark finished costs to see whether I'm way in over my head thinking about the idea of building vs. just buying.

We're in VA near Fredericksburg.  What I had envisioned is a single story home in the 2300 sq ft range with a 2 car garage; then comes all the questions.

Assuming the lot is amenable, I'd love a basement for utility and storage but don't know the average addition in cost for the excavation and forming which is also tied to the next question...

What to build with?  I live in a 2x4 townhome right now and in winter we're always cold.  Partially due to the old HVAC which I've been remiss on replacing, some is the fact the attic could stand to get a topping off of some blown in and some because the walls just seem to radiate cold (doors and windows have been replaced).

When I started looking at building all the new techniques and methods became overwhelming.  The idea of something like APEX or RASTRA blocks is very interesting but then the cost starts creeping up.  SIPS of some form (I see a lot of folks talking about using them for roofing) maybe or do I stick with stick built and go 2x6 with spray in insulation? 

Really I'm trying to get my bearings for what it will cost to finish the house.  I guess I'm looking for a 'best bang for the buck' solution.  I talked to one ICF builder in the area and he said it'd be roughly 265k for a house like I'm looking at, but that's just for the building, not the finishing which puts the whole project out of reach.  My top end range for completing the entire project (as in move in ready) for 100-110 per sq ft (not including the actual land purchase and with wiggle room for lot prep and utility work).  If the basement is feasible then I could reduce the house size a little into the 1900 range and go a little higher on the finished per sq ft cost.

Another thing I've come to realize is, I'm not exactly sure how the outside interior walls get finished vs. the costs.  As in, I've seen one install manual that has the guys just gluing/mudding the drywall right to the wall whereas my gut says that's going to suck for being able to attach anything to the outside walls.  The only other option would be framing inside the finished outer wall which is going to jack the cost nearly double for the work and materials. 

So...yeah a whole lot of what and not much to go on because I'm over my head.  I'd appreciate some suggestions, reading info to straighten me out or just hard facts.

Code min walls under IRC 2012 (not yet code in VA) would be 2x6 w/R20 cavity fill (open cell foam or cellulose would get you there), or 2x4 R13 + R5 of continuous insulating sheathing. Both work out to ~ R13-R15 "whole wall" after thermal bridging.

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

ICFs tend to start at R20 these days, but there are still R16 versions out there, (not that it saves you much to cut back that inch of EPS foam), but any way you cut it building with concrete is usually going to be more expensive than with stick-built, even if you fattened up the framing with better-than code exterior foam to meet or beat the thermal performance of the ICF. It won't be as quiet, and not nearly as hurricane-proof as ICF, but in thermal bang/buck, a 2x4 wall with open cell foam or cellulose with 2" of exterior foil-faced rigid polyiso will usually match or beat a minimalist R20 ICF on energy use & comfort, at the same wall thickness as a standard 2x6 framed building. The whole-wall R (after thermal bridging) is about R22 if you use iso (recommended), and the exterior foil facer adds another R1-1.5 average performance if there's at least a half inch of air between facer and siding. It's no superinsulated building, but it's way better than code, and no fatter than a code-min 2x6.

If you do the basement with an R16 ICF, it's dead-easy to make exterior EPS of the ICF co-planar with the sheathing foam, with the foundation sill resting fully on the concrete. When you do it that way there is continuous insulation from the eaves to the footing, no thermal bridging except at the window bucks/etc, but you might want to add 3" of open cell foam (or 2" of closed cell foam)on the interior of the band joist out to over the interior EPS of the ICF to air-seal & thermally break the foundation sill from the concrete as well.

Under the basement slab it's worth putting 2" of EPS or 1.5" of XPS that runs all the way to the interior EPS of your ICF. Even though that has a lousy return on investment from strictly an energy use point of view, it's HUGE on eliminating mold issues related to a cool-slab encountering humid summertime air, and the warmer-in-winter slab is more comfortable under foot to boot.

Air sealing is your friend- the cheapest energy performance boost you'll ever buy (and would be necessary to meet IRC 2012 max spec of 3 air exchanges per hour @ 50 pascals pressure, or "3ACH/50".) It's not rocket science, it's goop science, and it helps to start with layers labeled as the primary air barrier, from the vapor barrier under the slab to the ceiling under the attic insulation, primary vapor barrier layers need to meet and be correctly caulked/foamed etc as the thing comes together. (I prefer to detail the structural sheathing as the primary air barrier, but also air seal housewrap and exterior foam layers individually.) A bead of acoustic sealant between sheathing and framing as it goes up works, as well as between double-up studwall plates, and between bottom plate & subfloor, etc. FrothPak or can foam all electrical & plumbing penetrations of the sheathing, but also penetrations of stud bays at the studs & plates (yes, even wiring runs between stud-bays, unless you insulate them with open cell foam.) FSK tape the exterior iso seams and foam-seal the edges, take care to lap and tape every seam & tear in the housewrap, and all window & door flashing to the housewrap.

Every cable-guy plumber & electrician is out to screw you up on this, so somebody has to be the air-sealing czar (even if it's you), but with diligence you can usually get it down to under 2ACH/50 without a huge material or labor expense.

As an economic sanity-check see Table 2, p 10 of this document (and read at least the first chapter):

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

You're in climate zone 4, and those are "whole wall", not center-cavity recommendations, so the wall assembly, basement, and slab-R suggested above are in that range, definitely not overkill when done using least-cost methods. The up-costs of taking it that far above code won't affect it's resale value, but it will DEFINITELY improve comfort, and some of those costs can be balanced against the smaller heating/cooling equipment that it would take.

Getting peak heating loads down to under 10 BTU/ft is pretty easy on thiis type of house at your +14F 99% design temp, which means with an open floor plan and better-than-code windows you'd be able to heat & cool it at VERY high efficiency with ductless mini-split technology. If it has doored off spaces to higher-loss rooms you could do a ducted system, but they're typically more expensive and lower efficiency than if you can get by with 3 or fewer ductless heads. In your location/climate the heating efficiency of ductless heat pumps rivals that of (far more expensive) ground source heat pumps, and can be as cheap to install as the combined cost of a gas furnace plus standard central-air system, and cheaper to operate. But it only works really well in higher-R than code houses.

See also:

http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/high-r_value_walls_case_study_2011.pdf

The wall assembly I described is a 2x4 variation of case 2a & 2b,(without the advanced framing features) but with R12-R13 iso rather than R5-R20 XPS, and different cavity fill. Table 3 gives comparative thermal performance numbers, and the difference cases are discussed in excruciating detail (including moisture performance, buildability & cost) in rest of the document. The discussion of case 2 is in section 1.2 p35 (pdf pagination)

Dana,

Those two PDFs are amazing, thank you.  They will serve me well when discussing options.

My main concern at this point is really still the cost feasibility.  It would seem that the only way to find out will be to elicit the responses from some local builders; I just hate taking folk's valuable time just to find out I'll never get off the ground.

ETA: I just found this and going by the explanations of the different classes of building, I'm way over budget if I want something useable.  I need to significantly downsize or go with lower quality build options.  Really defeats the purpose of the whole build it your way bit...

Your link is broken... can't read it.

Apparently that site doesn't like you linking directly to the app page.

http://www.building-cost.net

The free calculator at the top center frame of the page.

Tom Bodet,

You might want to find another calculator. If I built that in my area of NC I would make at least $300,000!

richm

Rich, could you be more specific?  The options are really wide open with that thing.  Just slightly adjusting the foundation, roof and wall 'class' options I saw differences of over $100k.  Bringing down the overall quality got me into the mid $300s but that's still not low enough for me and probably doesn't cover the better build options Dana has been pointing out.

Tom,

You are right - really wide open with much in-between interpretation. According to this tool using better building techniques jumps prices drastically.

Using mid range without highly efficient walls or roof and standard finishes the cost for 1200 sq ft came to $464,000. That is very high for this area of NC - normal would be more like $150,000. A really nice 2000 sq ft 1 1/2 story craftsman style house on an in-fill lot in Raleigh might go for $200,000, and that's just building to Code.

I have found in the past that books like this tool is way too general. It may work great for some areas of the country but none that I have ever been in (upstate NY, VA and NC). I did not look at a publishing date for this tool - might make a small difference.

This tool kinda smells like some reporter or editor who knows next to nothing about building science writing an article about highly efficient construction methods after interviewing one source (who obviously would be bias) and stating it is the latest and best building method.

Maybe some of the builders here on GBT will respond with a better tool to guesstimate construction costs.

Rich

Buying an existing home will probably be much more cost effective. Of course buying something already built is also the most ecological, since the resources have already been used. I have no idea what homes sell for in your area, so I might be completely wrong, but in my area buying cost was about half or 2/3rds of building cost. The reason I built was because I already owned my farm and wanted to put the house on it. I even looked into buying a house and moving it to the farm, which was feasible up until the point of the utility company having to take down and replace all the wires along the roads, and that is the point it all fell apart.

That said, buying a modular can be very cost effective. Look for a modular builder who will let you custom design the house to your specifications, and one that has embraced green technologies. I ended up building a hybrid - stick built ground floor, modular main floor.

-Rosalinda

Posted By richm on 14 Feb 2013 05:23 PM
Tom,

You are right - really wide open with much in-between interpretation. According to this tool using better building techniques jumps prices drastically.

Using mid range without highly efficient walls or roof and standard finishes the cost for 1200 sq ft came to $464,000. That is very high for this area of NC - normal would be more like $150,000. A really nice 2000 sq ft 1 1/2 story craftsman style house on an in-fill lot in Raleigh might go for $200,000, and that's just building to Code.

I have found in the past that books like this tool is way too general. It may work great for some areas of the country but none that I have ever been in (upstate NY, VA and NC). I did not look at a publishing date for this tool - might make a small difference.

This tool kinda smells like some reporter or editor who knows next to nothing about building science writing an article about highly efficient construction methods after interviewing one source (who obviously would be bias) and stating it is the latest and best building method.

Maybe some of the builders here on GBT will respond with a better tool to guesstimate construction costs.

Rich

Thanks Rich, that's the kind of background I was looking for just to give me perspective on your comment.  Makes sense to me and you're absolutely right; the date of the base material and their attempt at generalizing costs will definitely skew the results.