Sorry, styrofoam or equivalent is a better idea, in prefabricated
panels or subassemblies, R-30 walls and R-50 roof. Try to catch This
Old House somewhere---they are doing one of these buildings, although
it is a ridiculously large monster.
My personal experience with peripheral-insulated slab construction
makes me quite fond of it, although some people like basements. Does a
nice job of air conditioning, and smoothes out rapid ups and downs of
Also, some kind of heat pump.
Thanks, I'll try to check that out. Here in NC, we have a "healthy
built home" certification that provides guidelines for defining their
standards, and there is a whole section on insulation that calls for
"rigid insulation", but the rest is greek to me.
"Rigid insulation installed as a thermal break at the slab edge
(R5, 6" minimum, vertically installed)."
On the one hand, I should probably not micro-manage and just trust
that the standards that are in place are good ones, but I'm just
trying to define some "must haves" for homes that may not meet the HBH
standards, and to address the variances within the standards.
For example, some certified homes have bamboo floors while others have
concrete floors with radiant floor heat. All have heat pumps and dual-
flush toilets and some solar-assisted heating.
Haven't seen any basements, but most houses in the South don't have
Yes I know it that's why I said or "equivalent", meaning rigid foam---
but ok, it isn't exactly equivalent. :-) I'm not sure what is used in
prefab panels---it used to be mostly styrofoam, but I would specify
isocyanurate if I were having a custom building.
I figure ta will do some research.
I am comparing two spec houses (not custom):
House1: solar-assisted hot water, isocyanurate insulation,
"sustainable" oak flooring, low E windows, dual-flush toilets, hardi-
board exterior and (surprisingly) a basement.
House2: solar-assisted hot water, blown cellulose insulation (which is
touted as coming from recycled newspaper), stained concrete (radiant
heated) and bamboo floors, dual-flush toilets, and hardi-board
exterior. Basement is an optional upgrade.
House 2 is more expensive.
Yes, still doing research.
I'm not sure what you mean by spec---are they built? If so, you can
hardly have an optional basement ;-).
My inclination is to think about what would be an ideal---that is, go
ahead and design a 'green dream house'---as a way to learn about the
various factors and their relative merits and value to you. Builders
are going to mix in 'features' just the way auto companies have
options in packages, and it usually isn't worth the money.
I have researched blown-in cellulose as a retrofit, and the underlying
problem is in the application---works fine as long as it is done very
well, but you're not going to know up front. Since you are in a
future tropical zone if AGW goes on, you should think about AC more
than heating. That's why heat pump may be your best choice. Also
what is R-value claimed and how do they justify it? Solar hot water
is a great idea---wish I had it.
Stuff like bamboo floors doesn't sound like it matters that much
really---is it supposed to be greener than oak or southern pine?
It's optional on the ones that haven't been built yet. It's a
House1 is heat pump and House2 has mini-split a/c (this house is
From House2 specs:
"All exterior walls, and interior walls to unheated spaces, will be
insulated with blown cellulose R19. The ceiling/roof assembly will
have 12 cellulose insulation R38. All wood-constructed first floors
will have R19. All internal partitions around bathrooms, powder
room, and Master Bedroom shall have R11 high-density batt sound
insulation. All windows and door jambs will be sealed. The exterior
walls are 7/16 ZIP System Panel with STORMEXTM water-resistive
Don't have the specs on House1.
Yeah, I'm trying to find out about reliability and maintenance costs
etc. These systems have natgas backup.
Generally, I believe bamboo is considered to be more "sustainable"
since it can be replenished more easily and more quickly, and it's
easier to harvest, and the oak in this case is FSC-certified.
I agree, it's not one of the more critical considerations, although I
currently have bamboo flooring and, irrespective of any environmental
benefit, I simply like the appearance better than oak.
I don't want to get into one of those philosophical definition things
with you ta,;-) but I don't think R19, which is the legal
requirement, can justifiably be called 'green'. Seriously, you should
refine the question somewhat.
If the goal is to reduce energy consumption and associated
consequences, then the thermal balance of the structure is the big
deal. R30 walls and R50 roof will keep you cool in the summer and
warm in (what you guys call) winter. Thermal mass, orientation of the
structure, shading and working shutters, and so on, will also make a
real difference. The *type* of insulation is irrelevant, as long as it
functions properly over the (long) life of a well constructed
There is such a thing as a 'really' green house, but it's not likely
to be found in one of those developments---although maybe the
construction and environmental group people can give some
Well, as I hinted at earlier, I wouldn't know an R19 or R50 from a B52
or an F18, so I'm just going by the "Healthy Home Built" standards
that exist in NC. These are the standards that are used to define what
is minimally "green".
Hey, we have "skiing" in NC and everything.
Well, the NC Healthy Built Home standard is probably just a minimum
requirement for marketing purposes, but there is still some merit to
the standards. At minimum, these standards ensure the homes are
"greener" than your average home, if not ideally "greenest", by
whatever standards those might be.
Obviously price is a major consideration too. If I was going to build
a custom home that was maximally "green", then I presumably could
afford to do all kinds of things.
I realize these "green" developments don't represent the ideal, and
that there is probably some marketing fluff in there, but that's kinda
what I'm trying to sort out . . . whether the "green" features are
actually worth the premium.
You apparently believe that the features I listed are not enough to
make it "really greann". So then what would you consider to be a
"really green house"?
OK, I see the problem. Are you saying that these HHB standards are
*not* a requirement? I thought they were part of the state building
code. Your first step is to sort out what's what; I thought most
codes already specified R-value, for example, as a result of the last
energy crisis. So if someone is claiming that baseline as a marketing
feature, I would stay far away from that builder.
NC has a green homebuilder certification program called "NC Healthy
Built Homes", which establishes "green" standards that, in many cases,
go beyond the normal state requirements, or have additional, more
stringent requirements (but again, not being a builder or engineer, I
really don't know what the differences are in some cases, such as
"The NC HealthyBuilt Homes Program provides a certificate for homes
meeting "green home guidelines" built by residential builders who
practice sustainable, high performance building strategies making the
home a comfortable, healthy and affordable place that reduces energy
and water usage, promotes renewable energy use and helps protect the
land where the home is built.
In a HealthyBuilt Home, building materials and processes are selected
to reduce pollution and the waste of natural resources during the
manufacturing and construction phases and throughout the life of the
home. The builder is encouraged to provide homeowner education about
the high performance features of the home and provide local resources
for "green" living."
The standards list everything from insulation to water usage to
landscaping to indoor air quality and so on. The standards are listed
So I am comparing two homes built by two different builders, both of
which are "NC Healthy Built Home" certified, but each has varying
implementations of the standards. In comparing the two, I'm trying to
discern which features provide the "most bang for your buck", as I
IOW, I'm trying to separate the fluff from the real "green" stuff.
You have pointed out that the R19 requirements are not really that
green at all. So I'm curious as to what other features you think are
required in order for something to be considered "green".
Ok I checked your state site and you apparently *don't* have a
statewide mandatory code for 1 and 2 family dwellings.
I think that using minimal non-renewable energy is the goal, and you
end up somewhere along that spectrum. The 'features' I listed above
tend to make you much more comfortable while using less energy---much
less if you do all of them; probably half as much as the house you are
Using less water is nice as well, but that isn't very difficult or
costly---we have a very expensive toilet and a very cheap one, and
they both use the minimal amount of water and work fine. Next step is
composting (waterless) type, and that ain't happening. Likewise, low
flow showerheads and faucets and so on are all out there and just as
cheap as anything else---probably because here we do have state codes
that require their installation.
So I would classify most other things as fluff, and I would question
lines in the spec that say "doors and windows will be sealed", since
that is just standard construction anywhere. In fact, I think I will
add long-lasting quality construction that doesn't require constant
maintenance and replacement to my 'green' requirement; one house every
100 years is much greener than one every 50. And that's another
reason that factory-built structures are a better deal.
Which features were those? Is that what you're referring to?
I really don't follow as to where exactly I would gain this 50% more
efficiency based on what I've said.
Re: insulation, going by this R Value Calculator (http://
www.jmhomeowner.com/betterliving/energyefficiency.asp), the R19 walls
are rated "Good" with R21 being "Best" -- I really don't know how much
difference it would make between R19 and R21 tbh). The ceiling R38 is
rated "Good", "Better" and "Best" (R38 is the only value listed). The
downstairs floors have radiant heating, but the upstairs floors are
R19, which ranks below their R30 value of "Good" and R38 of "Best".
But I'm not sure if the radiant floor heating in the downstairs would
affect their insulation choice in the upstairs.
Right, I noticed some of the standards seem rather common sense.
Well, sure, but the question is how can I determine whether the house
is of "quality construction".
Both of the homes I'm referring to are not "factory-built structures".
These are small, private, locally owned builders that live in the
neighborhood in which they are building these houses. We're not
talking about huge tract developments where corporate builders like
Pulte and such throw up 150 houses in 3 months and move on to the next
hunk o' land. (I live in one of those houses now, and it is definitely
not "quality construction", but the only way I came to discover that
was by living here).
The one project has 12 single family homes and the other has a mix of
duplexes and single families for a total of 15 units -- both are
infill development projects in walkable communities right in town.
We're talking low-volume, small-time local builders here.
I notice you're cross posting to several groups, I'm limiting my
response to construction types..
Firstly, insulation is not generic. Dense packed cellulose, if that's
what they're using for the walls, is much, much better than
fiberglass. Fiberglass loses R-value as the temperature goes down.
Cellulose does not. Dense cellulose minimizes air movement through
walls, fiberglass does not. Cellulose "buffers" moisture (a good
thing), fiberglass does not.
Second, there was a comment along the way about sealing windows and
doors. This is NOT standard practice. Builders think it is, but every
house I analyze has windows and doors installed the same way - they
shove fiberglass in the opening between the framing and the door,
thinking that will help the insulation in that space. It does nothing
good. Proper sealing of the window or door involves filling the entire
gap with a low-rise foam that insulate and air seals. If they are not
installed completely air tight, you can install the most expensive
window and it will perform little better than a cheap one. You also
run the risk of wood rot as moist air works its way into or out of the
Third, R-19 vs. R-21 wall insulation. Again, the type of insulation
makes a difference. Also, an R-whatever wall is not really that R-
value. You could put insulation rated R-19 into a wall with 24" stud
spacing and that wall will be better insulated than R-21 in 16" stud
spacing. If it were an option, you should have whatever R-value in the
wall plus use taped, insulated sheathing on the outside. This will
give you the best overall R-value for the wall structure as it
minimizes the "thermal bridging" at the wall studs". That is a very
good bang for the buck as adding R-7 insulated sheathing could
increase the overall R-value by about 50%.
for a very good discussion of these factors.
As others noted, in your climate, go with as much insulation in the
attic as possible. You get a lot of heat and regardless of attic
venting they put in, you're going to have a boiling hot attic. Pay
extra for added attic insulation. R-50- R-60.
Again, air sealing is a key part of the construction, especially in
the attic. Before the insulation is installed, you need to make sure
that all the holes between the house and the attic are sealed air
tight. That means every electrical wire, pipe hole, etc. should be
sealed. Also, if you have a choice - don't use recessed lights.
They're one of the biggest holes into the attic that you can have. No
matter the rating, I've not seen a recessed light that doesn't leak
like crazy. Use surface mount or hanging lights. The fewer holes
through the ceiling, the better. And any holes that are there, seal
them up after the electrical work is done.
Light colored roofs make a difference in attic heating.
All the other basic stuff everybody says - front load washers save
tons of water and get out more water so you need less drying. Smaller,
over/under style fridges can be much more efficient than side by side
models. A heat pump water heater (very few on the market) would be
great in your climate and would reduce water heating energy use by
1/2. Heat pumps for the house are great in a tightly constructed
house. And don't forget about an HRV or ERV, which is a necessity in a
tight house (google it if you don't know what it is).
I can only answer the very narrow question about the actual structures
and their relative merits in terms of (non-renewable) energy
efficiency. You clearly get points for walkable and infill, for
example, but what are we comparing it to? The same problem exists
when you talk about cost---are you going to be using coal-fired
electricity with no carbon tax? Are you thinking of resale value in 10
years when energy costs may include what are now externalities?
All too complicated for me.
But I would guess that, even in NC, the house you describe would use
twice as much energy as the house I describe here:
1) R30 prefabricated wall panels and R50 prefabricated roof panels.
2) Heat pump
3) Slab foundation perimeter insulation only.
4) Interior walls 5/8 gypsum, tile floors where functional.
5) High efficiency lighting.
6) High efficiency windows with external shutters, skylights.
7) Structure orientation and shading non-random.
You get the most savings with 1, perhaps 30% or more of the heating
and cooling. Each other thing contributes some percentage, and that
depends on lifestyle to some degree---you might get a total more than
50%. I'm also not familiar with your climate, but as I said somewhere
I am thinking that cooling is more important than heating. That would
influence my choice, for example, about the radiant floor heat
business. Those are getting popular now but I'm not convinced; I would
like to see radiant heat that is in the ceiling of the downstairs and
floor of the upstairs, for example, which would also serve for
I think the other stuff is fluff, as I said. Is cellulose 'greener'
because it is recycled? I don't think so, really, because if it
settles and loses R-value---which it probably will---you have a big
tradeoff. What about the CO2 transport cost of bamboo v native lumber?
And so on.
I know this may not help since you don't have the choice to build 'my'
house and you might have different tastes. But you shouldn't just take
the builders at their word, because the numbers get played with a lot.
For example, the claim of R19 by itself is meaningless---it may refer
only the insulating value of the 6" glass insulation, where a 4" wall
with foam sheathing and insulated vinyl siding could be rated the same
but yield better results.
I'm happy to try to give some guidance if you have specific questions.
I've read mixed reviews (again, I'm very early on in my research and I
am starting from basically point zero) so far of prefab walls. Most
recently, I was reading this highly critical analysis:
Feel free to add your counter-arguments to theirs if you wish.
Secondly, regarding R-levels and insulation, I've talked to several
insulation experts (i.e., people who are not in any way associated
with the builders and who would actually be motivated to upsell me),
and each of them basically said the same thing, which is that anything
beyond the R19 walls and R38 roofs spec'ed by the builders would be
overkill and not cost beneficial. For you people who have for some god-
forsaken reason made the dubious decision to live in the Arctic zone,
perhaps the R38 and R50 levels you mentioned might do some good, but I
really don't know. ;-)
I also talked to a local Energy Star certifier, and he went as far as
to say that the R-levels are not irrelevant, but a comparably minor
consideration compared to the sealing of the house. The Healthy Built
Home certification mandates that these homes are Energy Star certified
as part of the process, so they would be sealed using the highest
standards and inspected appropriately.
In either case, I am pursuing the question with another individual who
certifies homes for energy efficiency.
On a side note, according to the individuals I spoke with, NC does
have mandated residential building codes (R11 for floors, R13 for
walls, R21 for roofs, if memory serves me right). In either case, the
levels on the two homes I referred to exceed the minimum levels
enforced by the State.
I really can't argue the comments made above; I'm just passing on the
information. In any case, this is all very good because it makes a
perfect launching pad for discussion/research on my part.
Check (on House1) ... mini-split a/c on House2
I don't think this is feasible with 2X6 framing, is it? Why tile
floors over concrete?
Check. Energy Star certified.
Check on windows (Energy Star certified), don't think so on external
shutters and skylights.
Both homes are roughly North/South facing. I don't know what "shading
That didn't seem to be the opinion of the folks I spoke with, none of
whom are affiliated with the builders in any way, but I'll keep
In Western NC, the average high temps in the dog days of summer are
around 80 and the average low temps in Winter are around 30 (the
skiing ain't that great, I'm sure). In fact, it's not uncommon at all
to find houses that have no A/C at all.
Bamboo grows in NC and other parts of the States, but I'm not sure
where these particular floors are coming from - something to
investigate. The ones I currently have were manufactured in China, I'm
pretty sure. The oak floors in House1 are FSC-certified, but I'd have
to investigate their source of origin.
Well yes, why do you think I started the thread? ;-) I'm seeking out a
number of different sources of information, as I always do.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.