I’m getting some quotes from modular home dealers on replacing my fire-damaged Colonial with four new modules on my existing foundation.
I’ve received some basic floor plans and details and I’m wondering how much I can influence their “standard” build specs to perform more like a Pretty Good House?
I just finished reading the PGH book and noted all the detail in the specific wall and roof assemblies, etc. I don’t want to micro-manage the builder to that level, but I’d like something more energy efficient than a code-minimum home.
Are there some recommendations for low-hanging fruit that I can suggest to the modular dealer?
So far I’ve heard back from Excel Homes, Champion Homes, and PBS, all in Pennsylvania.
Here is the standard spec sheet from PBS:
CONSTRUCTION
2×10 floor joists @ 16” o.c. (12” o.c. for 15’9” wide modules is recommended)
Southern yellow pine (SYP) double perimeter band joists
23/32” tongue and groove O.S.B. floor sheathing, glued and nailed
7/12 non-storage rafters @ 16” o.c.
7/16” O.S.B. roof sheathing
Shingle-over ridge vent (full ridge standard for proper venting)
10” eave and gable end overhangs
8’0” ceiling height
5/8” type “X” ceiling gypsum board
2×6 exterior wall studs @ 16” o.c.
7/16” O.S.B. exterior wall sheathing
2×4 interior wall studs @ 16” o.c. (2×6 plumbing walls)
2×4 mating wall studs @ 16” o.c. with non-structural sheathing
1/2” wall gypsum glued & screwed on all walls, with additional foam adhesive applied on bearing walls
INSULATION
R-38 fiberglass ceiling insulation with vapor barrier
R-21 high density fiberglass exterior wall insulation with vapor barrier
Wind barrier house wrap
EXTERIOR
Certainteed Mainstreet vinyl siding in double 4” Clapboard or Dutchlap
Tamko Heritage 30-year architectural shingles
15# shingle underlayment & ice shield installed per code
Aluminum drip edge and 6” fascia
Vented vinyl soffit
ADDITIONAL TWO STORY SPECIFICATIONS
2×6 ceiling joists @ 16” o.c. with double 2×10 perimeter band joists
2×4 mating wall studs @ 16” o.c. with non-structural sheathing
Fiberglass insulation along exterior perimeter between floor and ceiling
Second story horizontal plumbing lines ran
All second story siding shipped loose
Stairs to second story installed (carpet and pad shipped loose) – floor plan dictates
Revised
Replies
Factory built houses come with a certification, which means the quality control of the units happens in the factory and they are not site inspected. So take that as you will. You will have no oversight of wall insulation, air and vapour barriers, etc.
The elements that are site constructed will be within your control, and can be upgraded. You can insulate the foundation to your liking, seal the building to the foundation, and control roof construction. An easy upgrade would be to install better than code attic insulation.
I'm not so much concerned about quality control (I trust the factory inspection process) but rather how to ask for upgraded build specs. In the PGH book, they talk about double-stud walls, and Larsen truss walls, and better-than-code vapor barrier assemblies, etc. I don't want to micro-manage their build process to that level, but pay for an upgrade as a package, so to speak. I'm not sure how to ask for that
You're more likely to have success with typical factory-built homes if you ask for exterior insulation. Or find a prefab company that specialized in high performance, such as these in New England:
Unity Homes
GO Logic
Ecocor
BrightBuilt
I would be careful about trusting the factory inspection system if the company isn't used to building high performance homes. I have seen some horror stories.
A reply from the author himself! Thank you for the book
I spoke with Unity and they were unwilling to set a modular on an existing foundation.
Will contact GO Logic and Ecocor on your recommendation
BrightBuilt sent me some options and a general estimate of $450-500 per square foot which frankly shocked me.
If that's the budget for a high-performance home there's no way that's in my budget, even with a generous insurance settlement.
You're welcome! I'm not sure if you'll find GO Logic or Ecocor to be any less expensive than BrightBuilt--they both focus on very high performance and are generally competitive with what it would cost to build the same thing on site. The main benefits are a short dry-in time and good quality control. And if you don't have high-performance builders near you, they fill a niche.
At the risk of veering off into politics, I hope that high performance homes aren't just the domain of the wealthy.
We are firmly upper-middle class, with two professional salaries. There's no way a $1.5M home is within reach for the vast majority of Americans. I respect the rights of builders to cover their costs and make a profit, but how will they upgrade America's energy-wasteful housing stock if so few can afford them?
It all depends what's important to you. Around here, high-quality homes start around the same price; the difference is what "quality" means to you. It can mean having a lot of different rooflines, oversized windows and custom cabinetry, but average (or worse) performance. Or it can mean a simple, straightforward design with budget-friendly materials, focusing more on health and energy performance. If you want the large windows, fancy trim, complicated rooflines AND high performance, you're going to pay a premium, there's no way around it.
If, on the other hand, you're comparing PGH to a "starter home," which around here is often a modular double-wide with 6" walls insulated with fiberglass, commodity OSB sheathing, a budget WRB, vinyl siding, 2-pane vinyl windows and a mix of cheap carpeting and vinyl flooring, and a cheap, loud bathroom fan to provide "ventilation," there's no "slop" to pay for the higher-quality, longer-lasting, more-durable and lower-emission materials.
Pretty Good House isn't forcing anyone into anything. It provides a framework on what to consider when making the thousands of decisions that need to be made when designing and building ANY house. If you don't want to, or can't, pay more for better materials, then go with code-minimum, it's up to you.
yes, simple, durable and efficient is what we're looking for.
I don't want a multi-peak McMansion with a lawyer foyer.
Footprint is a four-corner rectangle Colonial. No dormers or gables
If you were ranking upgrades from a "code minimum" house, where would you prioritize?
"6" walls insulated with fiberglass, commodity OSB sheathing, a budget WRB, vinyl siding, 2-pane vinyl windows and a mix of cheap carpeting and vinyl flooring, and a cheap, loud bathroom fan to provide "ventilation,"
If cost is paramount and environmental impact is not a priority, my go-to assembly is Zip sheathing over a 2x6 wall insulated with fiberglass, with exterior polyiso foam. We need at least 2" of polyiso in CZ6. I'm not opposed to vinyl windows or vinyl siding when the budget requires it. Focusing on air-sealing will have the biggest impact.
Hello! We are in the same boat. Our 1,350 sq ft double stud wall ranch was destroyed in a fire in December. Our insurance company wants us to keep the slab with the plumbing and radiant heat in it, but that pretty much eliminates modular as an option. Unity told us the same thing. How has your search gone?
Understand they have an assembly line and are unlikely to make any big changes.
I did not see anything on the spec sheet about the windows the most expensive line item in most any build. U value and frame materials are the big questions.
Is the furnace / heat pump upgradable or is that field installed?
After the home is completed consider having blower door directed air sealing done and inferred photo taken to spot any flaws.
Did the old basement have water problems?
Walta
sorry I omitted the line item for windows. I assume there are upgrade options for everything
-Fiberglass 6-panel front door w/ vinyl jambs & brickmould
-Fiberglass half-lite rear door w/ vinyl jambs & brickmould
- 6’ vinyl sliding patio door w/ low-e glass (floor plan dictates)
-Ply Gem Classic Series double hung vinyl windows – tilt sash, DP50, Warm Edge, low-e glass, Argon gas filled with full screens
I believe the HVAC is installed by the GC on-site. The modular company will need to accommodate for air ducts and chase in each floor. Planning on multi-unit ducted heat pumps, with resistance heat backup. Also will mainly heat with EPA wood stove as I did in previous house.
Yes I will insist on blower door test. Can I write a target ACH into the contract?
Old basement had a sump pump but it only ran heavily during spring snow melt. Otherwise no water problems. I will partially finish the basement again and insulate it better this time around.
“Old basement had a sump pump but it only ran heavily during spring snow melt. Otherwise, no water problems."
You may want to reread what you wrote. What I hear when I read this line is! Yes the old basement leaks but it only floods if the electricity happens to go out while it is raining.
How many dollars are you really saving by keeping the leak and damp old foundation? 10% maybe. How much have you compromised the floor plan to accommodate the old foundation? Consider if the old foundation is really an asset or a liability.
Do the windows carry a NFRC label that would be required for a field-built home?
All the words about the windows and doors sound nice but without the third party lab testing required to get the NFRC label the words are meaningless.
https://www.nfrc.org/energy-performance-label/#:~:text=The%20NFRC%20label%20helps%20you%20compare%20between%20energy%2Defficient%20windows,performance%20ratings%20in%20multiple%20categories.&text=U%2DFactor%20measures%20how%20well,is%20at%20keeping%20heat%20in.
Walta
thanks for the tip about the NFRC; I will be sure to check on that
regarding the foundation; I had the demo guy estimate $30,000 additional cost to demo the foundation, plus whatever it would take to re-pour it..another $40-50k?
That may be pocket change to some people, but it's real money to me.
The sump pump has a dedicated battery backup, and my whole house has a standby propane generator. So I'm not worried about flooding the basement. Just need to figure out how to insulate it.
Modular factories and customization are basically oxymoronic- the whole purpose of factory built housing to standardize the details, produce in volume, and lower production costs.
Many of these companies do offer a higher-end wall assembly with increased insulation values.
I have dealt with several modular projects in the last several years, and they have ranged from impressive to abysmal. Buyer beware.
"higher-end wall assembly with increased insulation values" yes that's what I'm looking for. An upgrade, rather than customization. I don't want to tell them how to do their jobs in the factory
Any tips on companies to contact or avoid? Private message is fine if you don't want to disparage them publicly
" I don't want to tell them how to do their jobs in the factory."
Then the alternative is to tell them what outcome you want.
Perhaps:
* A higher level of insulation than code minimum
* A higher level of air sealing than code minimum
* Better doors and windows than code minimum, both in terms of u-factor and air sealing
It should probably go without saying that this is done with appropriate weather barriers and vapor barriers.
I am in northern Canada, not sure my recommendations will be relevant to your situation.
The recurring theme for performance builds is to air seal. I doubt the prefab folks are up for the job plus you still have to take care of the joint between sections.
My thinking about this would be to get the pre-fab shipped without siding just house wrap. Once on site strip the house wrap, take care of any window flashing details, tape the seams of the sheathing, seal the sheathing to the foundation and ceiling drywall. Once nice and sealed up install new house wrap. You can add a layer of exterior rigid if your budget allows and install siding.
About 2.5" of exterior polyiso halves the losses through your walls but even less can work. Vinyl siding can be nailed directly through 1" of foam but that can be pushed a bit, for thicker foam rain screen strapping is always better.
yes I believe that's how the modules are shipped. I will have more control over the GC who can seals the seams and install exterior rigid insulation before siding
The basic problem is that modulars are all about up front cost and pg houses are about the long term. So you swim upstream trying to get the latter while paying for the former.
If you go the modular route, my guess is you don’t get to have any say over wall insulation. If they will work with you, I’d avoid fiberglass and opt for cellulose or rockwool.
I would pay up for good windows and balanced mechanical ventilation.
The modular homes that I’ve blower door tested and occasionally worked on have consistently had two areas of high leakage: where the modules join and the sill connection. Windows and doors are sometimes trouble also.
I’d pay attention to ventilation. Because these buildings have a lot of low cost man-made materials, I’d insist on an erv for fresh air.
I blower door tested a modular a couple of years ago that had a 120 cfm exhaust fan hard wired into the smoke detector circuit so it ran 24-7. This was a pretty ruthless code hack in two ways—it satisfied the requirements for mechanical ventilation and also artificially lowered the tested leakage rate. Of course air pulled through rodent-infested fg and vinyl siding and osb is not likely to be fresh, and the operating cost of dumping all that heated/cooled air is no doubt outrageous. The owner admitted he was planning to unhook it as soon as I left. But as a cheap way to satisfy code—well, that’s how it works. If the kids get asthma it’s unlikely anybody will connect the dots…