input & experience + conversation

[energy_rater_La]

I recently posted the following. and yesterday talked it over with one of the
guys who taught me a lot and encouraged me and my curious mind to continue in my field of work.
he agreed, although when I posted my take on foam & vs units it killed the
thread.

so ted, kevin, shophound and yes you david who thinks I need to
think about tradeoffs (although it is my sucessful business and
meets resnet and local gov program) let's talk about it.

Here is the post.
now foam insulation. open cell is the least expensive least R-value...but at 3x the cost
of conventional insulation..allows moisture to move through it.
closed cell causes water to become trapped has a higher R-value and is 4x the cost of conventional insulation.
when you calculate payback of foam insulation it is a long payback time. because of the cost of the material.

here is my take on foam..

if builders/trades people didn't cut holes in the ceiling into the attic and not properly seal them,
then you would have a continous air barrier between the unconditioned space and the conditioned space.
itrw, recessed lights are not insulation contact air tight..bath fans, stove vents are not sealed
to ceilings when installed.

no one seals the holes they create in the building envelope. this is a very important thing to do.

if architects and designers would put mechanicals and ducts into the
conditioned space instead of the most exterme temps of attics then ducts would perform better
and mechanicals would last longer and be easier to service.

but these things dont happen in the real world.(or not often enough)
I see fur downs & heating closets in older homes..but at the premium of giving up
sq ft of living space..not for new homes..unless plans are created with these things in place.

so as a result of these failures foam is a cure all.

by foaming the roofline you put mechanicals and ducts into a semi conditioned space
ducts are now under insulation not surrounded by 130 degree attic temps in the summer.

issues with recessed lights and other unsealed holes into the conditioned space
are no longer depressurized by hvac system reducing the air leakage from these holes into living space.

in my area it is near impossible to get a hvac company to do a comprehensive load calc.
and 2000 sq ft homes get 5 ton hvac systems every day. oversizing results in lack of dehumidification
due to short run times of system. these oversized systems cost more to operate, and have shortened useful lives.

so variable speed units have become more common. personally I think that the hvac industry
realized the oversizing problems and how difficult it is to get companies educated enough to make responsible decisons and said
"ok..lets make a system that
will run in a lowered speed that is what the house requires, but then when summer temps hit
90's will switch to higher speed so homeower will still be comfortable
and the company will not get a service call". (LOL!)
costs more, sure. but it is a bandaid for lack of education.
a good band aid. solves a lot of issues and is good equipment that works well.

same with foam.
can't educate builders, designers, architects & home owners to not put
ducts & mechanicals in living space
so let's make a product that takes these issues and makes them
less of an issue.

who pays? well homeowner buys more expensive hvac and insulation
to achieve what could have been achieved if everyone had been on the
same page to start with.

I guess I shouldn't say either are bandaids, nor lay the bulk of the blame
on these trades ..because I have had many ratings where the homeowner
insisted that the bigger the unit the better. wrong..and some you can educate
but others, you can't.
its more of an evolution. a timely evolution because we have the knowledge
to make more adaptable equipment nowdays.


A lot of changes come about because of failures.
Joe of building science always includes in his seminars that
you get experience from failures & mistakes. and he is very experienced.
so we make our own mistakes, and hopefully learn from them.
and if we are smart..we learn from other peoples mistakes.
this is true..and insightful. we can learn from others mistakes.
it wasn't just what your parents told you as a teenager, but a statement
that holds true in life.

old guys knew stuff..lots of 100 year old home without rain screens
and dedicated drainage planes behind brick cladding..just felt paper.
felt worked well, and still does. but we have become so enamored of
tyvek and 'modern' products that no one uses felt much anymore.
it is a progression..try/develop someting new..see in 10,20,30 years how
it has held up. progress.

personally I evaluate each home on its own. not compare it to one the same
size down the street..even if same design, same builder, same subs.
the subs may have been pumped for the first house and dog died
wife left..had a hangover for the next house. human error. completely
understandable.
and people live differently. a young couple with 3 kids
running in and out of house live differently than an older couple who
stay indoors most of the time.
its a challange to meet the needs of such a diverse group of clients.
but it is what makes live interesting, creates a need for my work,
and keeps me excited about my career.
not to offend anyone blah blah blah disclaimer.
__________________________________________________ _______
so fire away...but lets all keep an open mind. education is power.
and I won't cry if y'all disagree..but with 10+ years in the biz
and the resnet software I use...savings & payback is calculated.

and david..what is your background? you give good info sometimes
which makes me wonder if you are a HO or in the biz.

[Shophound]

One thing that has become more clear to me while engaging in this topic of discussion; a clear distinction between retrofitting an existing house and residential new construction (RNC). Some thoughts both ways:

Economy has RNC almost at a standstill. People may be still building, and if they are, they should think about building envelope issues. Energy will NOT get cheaper over the long haul. If it comes down to the best kitchen cabinets vs. mechanicals and ducts in the conditioned space, opt for the latter. The cabinets will be out of style in ten years, but year round the mechanicals inside the thermal boundary will pay HUGE dividends, both in terms of overhead savings and human comfort.

For builders/architects - either mandate as good building practice the use of airtight insulation contact recessed "can" lights, or STOP USING THEM!

If the ducts are out of the attic, the air handler is out of the attic, and the ceiling is monolithic with no penetrations (and all other wiring/plumbing penetrations through top plates, etc. are sealed) then do nothing different with the attic other than, say, R50 on the attic floor and good ventilation.

How much space does a mechanical closet eat from the floor's square footage - I mean really? 25? Whatever it is, add it somewhere else, and dump the giraffe foyer. Overall, we don't need ceilings that reside in the stratosphere. If you don't want eight foot ceilings, go nine. Just avoid fifteen or twenty.

Don't build a big space, call it a "bonus room', and do a crappy job accounting for how it affects heat gain/heat loss in relation to the rest of the house and HVAC system.

Shade the windows with the structure...please! Overhangs not only shade the structure, they reduce sunlight and weather beating the crap out of the siding.

Be a bit more reasonable with wall to window ratios. You can't get window U factors and SHGC high enough to justify a west facing, unshaded wall full of these units.

I can go on...and probably will...

I'll cover existing/retrofit next post.

[gwt181]

Energy_Rater_La

Do you feel like you’re on an island by yourself, I do.

You are correct with people in our area. Last few weeks while sitting at the refrigeration supply house I ask a several guys what load program they use. Most didn’t reply much just say that’s the salesman’s job. Some said you don’t need that. One guy said he uses a program that was given to him at a training seminar. He said most customers say no way that a smaller unit and fixing other problems in my house is going to work, I want a bigger unit. Companies and customers need to be educated.

I have fixed several units this year for sweating. Most were last year’s change outs with larger tonnage and old duct. I expect that number to double or triple next year.

This should be a good thread and looking forward to learning more.

[genduct]

Good jobs require Good (informed) customers. I didn't see you take the heat duct transfer into your payback calc or the better air barrier. But that being said, you know that the 2 part urea- foams of 35 years ago are still remembered by some and the same with the Dryvit disasters where someone didn't follow the spec but the whole world was questioned.
The foam products are just going to have to get less expensive to compete with the "safer" air barrier and traditional insulation approaches. that when done right also give good performance. The 3x or 4x is tough to justify/ sell

[energy_rater_La]

actually heat transfer & air barriers are accounted for in the software I use
for the state program/also the national software for energy raters.
heat transfer lowers the load, air tightness is entered in air infiltration
amount.

granted a big problem locally is that the foam sales folks want us
to 'give' the 2-3" of open cell an 'equivalent' value of R-30.

with my software, just like with a load calc..
the software requires actual R-value of
foam..and building tightness is entered in another screen of info.

another issue with foam is that not only does the mix have to be correct
but the temp. I was at a house for a final inspection. open cell foam
on rafters. the foam had pulled away from the rafters 3/4 to 1" in
approx 1/4 of the install. after much much hassle, foam company came
back and admitted that the mix had not had time to heat to proper temp.
and re-sprayed areas that had this issue.
but who did the research...me and the HO. had to send pictures and numerous
emails to the company to prove that their temp mix was the issue.
so now all is 'good' with me and foam company..but mainly the HO
has the install they paid for..I learned something and so did the foam company.
hopefully they will remember...I won't forget.

now I did see a house on piers where the foam mix installed
under floors was incorrect.
the foam formed honeycombs (pockets of air within the foam install)
because mix was incorrect. this was HO's buddy's install. fortunately
there was a guy not too far away who does top notch installs...
and he came and tore out and installed foam correctly.
this was an antebellum home...over 100 years old. utility costs
well.. just say in 17 months he could have bought a new luxury truck...
longer for a benz...60 months?

and Watson La...2 hours from me..give or take.
howdy neighbor....don't get me started on hvac supply house
conversations...but drop me an email I can give you info
that will get you into houses as a system instead of
insulation and hvac as separate parts.
houses have to work with all these components
and all too often they work against each other.
...and get your pro status..stat!


so we got off track from my original intent of this thread.
I'd like you all to re-read the first post and see if you
see what i do.
instead of folks building & sealing gaping holes in houses
..installing, mastic sealing and sizing central units it has
come to a point where mechanicals and products are being
developed to make these homes affordable to live in.
at a great cost (esp foam insulation) to home owner.
variable speed...great equipment hands down the best.
and thanks to the brains that figured it out.
foam...miracle insulation...well not so much.
high cost...promises of total air encapsulation
but when tested...in most cases partial encapsulation.
in my 10+ years of doing this.

new technology is driven by higher learning
and customer demand.
HO pays.
and should for better hvac, correctly installed sized and sealed.
but the foam...good product high cost often not air tight.
that is my bone of contention with them. it is not a fix all for homes.

shoot even Joe of building science got into trouble in a couple of
states with foam. and he knows a LOT of stuff.

so what do y'all think about the hvac & lack of duct sealing
with foam insulated rooflines? the 25-30% of duct leakage in
new construction semi conditions the attic. but if ducts were sealed...
and in existing homes...don't get me started. Y'all see the messes
in attics. ducts not attached..much less sealed. loops of flex
restricted air flow due to ducts being crimped..

It kills me that HO's can't understand the need for ducts and mechanicals
in conditioned space. this can be done in design stage. And that they
have a closet that would serve perfectly in many cases...but just won't
give it up...even though they have enough closet space to equal my
little house.

[pstu]

To me even a 10% duct leakage means 120 CFM on a 3-ton system, and that much infiltration powered by the HVAC fan is just appalling. Does anyone think I am picturing it incorrectly?

A builder near me brags about his construction quality and seems to say the right things. He is strongly against sealed attics, saying that structure damage from moisture happens A LOT in our hot-humid climate, and that many lawsuits are pending over this. He argues that with highly sealed ducts, RB and attention to sealing the attic/ceiling plane, you can achieve practically all the benefits using "ordinary" construction methods. I think he might be right.

Craftsmanship seems to be key to good results, in so many ways.

Best wishes -- Pstu

[Shophound]

If we're talking RNC, how about going with ducts and mechanicals below the attic, just as La said, and then build out the attic conventionally? Use RB on the roof deck, insulate to R50 on the attic floor, do not punch the ceiling below the attic full of holes like Swiss cheese!

If we're talking retrofit (existing house), weigh cost of foam vs. high IR reflective metal roofing materials, such as metal tiles or standing seam. If the roof cladding can be the radiant barrier, how excellent is that? Heat gain to ducts in attic greatly reduced, roof deck does not get ridiculously hot. Insulate attic floor to R50 to slow winter heat loss. Roof cladding lasts a lot longer than asphalt shingles, which are the worst thing ever contrived for a residential roof other than roll roofing or tar and gravel, IMO, pertaining to heat transfer and waste (roofing should last longer than 20-30 years, IMO).

[genduct]

Buddy, I hate to burst your bubble, but "sealed" residential duct is equal to unsealed commercial duct that is Leak Class 48 supply and 96 for return. this info is buried in J and D

What really makes me wonder is the building science and new IRC (duct blaster check) that puts all it's eggs on the leakage thing and what happens when that good "sealed" duct doesn't have air squirting out of the hole Which of course is the object of the exercise.

I guess it is no secret that I prefer ductboard with it's class 6 status. I have a similar experience with trying to "sell" what we do and funny thing is we are half the cost.
Go and Figure HUH

Good Luck

[pstu]

Buddy, I hate to burst your bubble, but "sealed" residential duct is equal to unsealed commercial duct that is Leak Class 48 supply and 96 for return. this info is buried in J and D

What really makes me wonder is the building science and new IRC (duct blaster check) that puts all it's eggs on the leakage thing and what happens when that good "sealed" duct doesn't have air squirting out of the hole Which of course is the object of the exercise.

I guess it is no secret that I prefer ductboard with it's class 6 status. I have a similar experience with trying to "sell" what we do and funny thing is we are half the cost.
Go and Figure HUH

Good Luck

It would benefit me if someone would step down and go over that lesson in more elementary terms.

Thanks -- Pstu

[genduct]

Back in 1981 we finally adopted the much more intelligent European approach to duct leakage. It is not helpful to use standards like 10% of fan airflow as a leakage goal. Leakage depends on how we build and seal duct seams and connector joints (A, B or C seal) how much pressure is in the duct 1/2 to 10 inches of pos or neg, and how many sq ft of duct is hanging off the system.

The leak class numbers of 3.6, 12, 24, 48 for commercial are simple. If you have 100 SqFt of duct with 1 inch of pressure you can EXPECT 48 Cfms with a leak class of 48

It gets a little complicated something like the Cfm50 testing you are familiar with, and that is WHAT DOES THIS REALLY MEAN. You know the "modifiers you use to "estimate the NAT infiltration Well how about the "average" operating pressure.

That is not to say it has no value, yes it does because we can get an idea of how well the duct is done. Using this info for modeling or estimating operating costs we, as you know that is another story.

SMACNA addendum to their duct construction standards deals with this in detail

[DavidNJ]

Buddy, I hate to burst your bubble, but "sealed" residential duct is equal to unsealed commercial duct that is Leak Class 48 supply and 96 for return. this info is buried in J and D

What really makes me wonder is the building science and new IRC (duct blaster check) that puts all it's eggs on the leakage thing and what happens when that good "sealed" duct doesn't have air squirting out of the hole Which of course is the object of the exercise.

I guess it is no secret that I prefer ductboard with it's class 6 status. I have a similar experience with trying to "sell" what we do and funny thing is we are half the cost.
Go and Figure HUH

Good Luck

Question: why don't you use Koolduct? Isn't it similar to fiber duct, just lighter, thinner for a specific insulation, and stronger? I believe Kingspan says they should be leak class 3 regardless of joint (http://www.koolduct.kingspan.com/koo...f/koolduct.pdf, page 16)

What about spiral duct? Gustafson rates some of their gasketed ducts as leak class 3. http://www.gustafsonduct.com/kcms.as...Ref=89&Area=82

What is IRC?

[genduct]

Ductboard is leak class 3, the "authority's down rate to 6 because they think the potential tie rod reinforcement "needs" that.
Still 1/8 leakage of "sealed" res sheet metal. After a while, just like R value, diminishing returns.

Dave we have discussed the KoolDuct issue. More expensive for an acoustically inferior product that has potential thermal bridging problems. And before you ask again, yes I know about tiger clips. I told you I would be happy to sell you what you want, I have 20K Sq Ft of the stuff in inventory and 7K lin Ft of extrusions. As you know there are only a few Koolduct people out there and you happen to be talking to one of the few.
Low pressure residential is not the place/ application where the product is cost effective.

If I was smart and not honest I would just agree with you.
Unfortunately I think, you think, the advice you get on this site is worth what you pay for it. At some point you may need to defer to someone who has the experience, perhaps then you can come to some conclusions.

[genduct]

Didn't notice the last question IRC = International Residential (building) Code.
Adopted and sometimes modified in most if not all of US. as contrasted to the commercial ver IBC and IMC I think you can guess what they stand for