Moving Attic duct work to conditioned space to save energy. Return on Investment?

[newstudent]

This house is in North Carolina, about 1800 square feet. Split 3 ton HVAC system with Gas Furnance. The attic is well vented with two power blower fans, but it still feels like an oven up there. I've asked a couple of HVAC professionals about moving my coil R6 duct work out of the attic into the conditioned space and they both kind of dismissed the idea, but everything I read online says it's one of the best energy efficiency improvements you can do.

the living room has a Cathedral ceiling so it wouldn't be that hard to drop the ceiling a little and get the main truck line into conditioned space.

In a totally DIFFERENT home which is around 1100 sqfeet we hired insulators to apply 8" thick fiberglass insulation and covered all the coil attic ducts. The ducts are now very cool. This document states 20% improvement.
http://www.nrel.gov/docs/fy10osti/48163.pdf

Thoughts on why installers are telling me this is not worthwhile, yet everything I read says it is? Who's right?

[dan sw fl]

This house is in North Carolina, about 1800 square feet. Split 3 ton HVAC system with Gas Furnance.
The attic is well vented with two power blower fans, but it still feels like an oven up there.

I've asked a couple of HVAC professionals about moving my coil R6 duct work out of the attic into the conditioned space and they both kind of dismissed the idea,

the living room has a Cathedral ceiling so it wouldn't be that hard to drop the ceiling a little and get the main truck line into conditioned space.

This document states 20% improvement.
http://www.nrel.gov/docs/fy10osti/48163.pdf
---------------------


I would not refer to one who makes a living in the HVAC industry AND dismisses the energy saving aspects of 'moving duct into a conditiioned space' as a Professional.

IT DEPENDS
on the Installation Costs to 'move the ducts into a conditioned space'.

First, spray foam the bottom of the 1,200 to 1,500 square foot roof deck may cost $ 3,000.

Your A/C Annual electric cost might be $450 (probably worst case?).
3. ton = approx. 3 kw/hr * 1,500 full operating hours for N.C.= 4,500 kW-Hr or $450 / year ( at $0.10 / kw-hr)

At 20% [15% on page 11 of linked article] savings .. .:. operating cost savings might be in the range of $90.
$3,000 * 2% = $60. interest. So, net savings = $30/ year.
So one could speculate that the R.O.I is about 100 years.

http://www.icynene.com/homeowner
Savings could be well above 20% due to reducing leakage.

In contrast, using your situtation of
Providing an additional 8" of blown in insulation might be in the ball park of $400. for 900 square feet.
Net savings are $90 - $ 8 = $82. .:. R.O.I. = 5 years.

... K.I.S.S. Example ...
K eep i t S imple & S incere

It all depends on installation cost and what one wishes to do based on their 'gut feeling'.

[newstudent]

Thanks for verifying what I thought. Instead of adding insulation, I think I'm going to get some drywall/framing guys to simply remove the duct work from attic and place it behind new framing and drywall. I don't like the industrial look of exposed ducting.

Unfortunately this is only easily done on one side of the house. For the other side I'll get the exsisting coil duct wrapped with some more fiberglass batts. It makes the ducts super big and bulky, but hopefully will save a lot of energy. R8 to R25

The HVAC system is 17 years old, when it is time to replace it, I might consider more improvements.

[energy_rater_La]

is the house laid out so that you can run ducts to all rooms?

to me, this is the most important question.

my ducts are all in fur downs inside the 76 degree conditioned space.
compared to putting the R-8 ducts into a 100+ degree attic..its
a no brainer. but then my house's layout is fairly simple and ducts
were easy to run to all rooms. also my ahu & supply plenum is in
conditioned space also.

in the past, I've worked with hvac companies to put ducts in furdowns
in conditioned spaces. most do not grasp the concept and you wind up
pushing their reluctant techs to do the job. at best hvac co running
ducts is done. then carpenter to build furdowns.

while my savings will be a little less than table 3 of the article you linked
this reduced savings is due to lower electric costs.
my software shows that putting ducts inside conditioned space is the
most savings..vs higher seer, eer, hspf or in your case afue.
as this install has a long life compared to life of unit, the cost to do this
install is spread over a longer length of time.

while using foam to create an unvented attic puts ducts into semi conditioned
space, it is once again a bandaid used to cover other issues.
and know that unvented foam sealed attics are semi conditioned.

things like duct leakage, house to attic leakage, and thermal bypasses
are made less of an issue when insulation/air/thermal barrier is moved
to the roofline, if these things were done properly to start with, by the
tradespeople, then foam wouldn't be the cure all it is sold to be.

then you have to factor in the problems with foam.
unvented attics that are not air tight, complicated rooflines and uneducated
installers, problems with chemical mixes & roof temps, roof leaks etc etc.
and the most common problem..'average' insulation depths. dips and bellys
between roof rafters, missed spots...and the story that 3" acts as R-30.
the R-value per inch of foam install has to meet code. meet code, not 'act as'.

in testing these 'unvented' attics over the past decade..most are not
what they are sold to be.

if you can't relocate ductwork, the easy out is to foam seal the attic.
most cases it is much better than vented attic with ducts in attic.
but be aware that foam companies are there to sell product. if no one
is testing or inspecting their work, someone with no dog in the fight,
you get what you get. not always what you were told you were getting,
or what you paid for.

this is why in my personal home, I first air sealed the attic floor, then
came inside the house and completed the air barrier. insulated attic
to R-30. put mechanicals and ductwork inside the living space.
I'm thrilled to have cut my utility bill by more than half.

when you insulate without air sealing, the performance of the
insulation is reduced by air moving through the insulation.
so rather than just blow and go..air seal first. or save your money.

I'm curious as to how you added 8" of insulation to ducts in previous house.
without having two vapor barriers on the ducts...how did you achieve this?

best of luck.

[54regcab]

I don't doubt a 25% savings, especially if you are moving the furnace into conditioned space. IMHO is should be code that the the equipment and ductwork be in conditioned space (this can also be done by foaming the attic). Would you be OK with one piece of exposed ductwork in the cathedral ceiling? this could save considerably on installation costs...

Most ductwork that is in conditioned space has the registers in the interior walls blowing towards the exterior walls. When buying registers get the commercial style that have the completely adjustable face. You might even be able to get away with less total registers.

[energy_rater_La]

cathedral would be furred down for duct. no visible ductwork.

[Shophound]

New houses should have all duct work in furred down enclosures, IMO. But so often how new homes are designed (really...someone actually designs those things vs. mere "cut and paste" out of a stock plan computer data base?) make it difficult to run duct regardless of whether it's in an attic, basement/crawl space, or even in conditioned space chases (aka furdowns). Fundamentally I believe house design needs to change significantly to return more comfortable, energy efficient structures, but current market trends still favor the McMansion layout, which has shown in my mind to be a world of problems due to the emphasis on appearance vs. functionality.

[newstudent]

I'm curious as to how you added 8" of insulation to ducts in previous house.
without having two vapor barriers on the ducts...how did you achieve this?

Basically the existing flex duct was sprayed with foam insulation and then reglular 6" thick batts of insulation were laid ontop of the flex duct.
Similar to this article below.
http://www.carb-swa.com/articles/gui...03_17_2009.pdf

Except my duct work is not Burried, it just sits on top of exsisting r30 insulation with a "blanket" over the top.

I check on condesation every few months, but have not notice anything bad so far. There's not much air movement so that probably helps.

[newstudent]

"is the house laid out so that you can run ducts to all rooms?"

Yes the AirHandler/Furnace is a horizontal Trane above the garage space (which is not furnished). It currently has a spider web of flex duct going to every single room.

I'd love to just rip it all out and start over with a vertical unit in the garage, but that is not going to be economical to do. While I can move a lot of the duct work INSIDE the conditioned home, the AH/Furnance and main feed and return lines will be stuck in the attic for now.

[energy_rater_La]

where are you located?
we can't bury ducts or even have ducts in contact with each other, because of humidity here in La.
even ducts lying on top of insulation on attic floor will condensate.


so your plan is to move some of the ductwork into conditioned space.
supply plenum (trunk line/plenum) will remain in attic.

with part of the ductwork in the attic and the main feed (trunk/plenum??) staying
in the attic..your will achieve some savings..how much?
depends. how much is moved inside, how much remains.
what effect does 100+ degree air have on plenum/trunk.

what I ment by how the house was laid out so that ducts could be run to
all rooms was this.
is the house configured so that you can serve all rooms by furring down a hallway?
these layouts are usually fairly simple
living kitchen den whatever as one end of the house and hallway to bedrooms
baths etc.

what you need is an area that can be retrofitted
(furred down)
so that ducts can run thru this centrally located
area to serve each room of the house.

in my house the living/office & br1 are at the front of the house
with kitchen bath & br2 at rear. furred down kitchen to serve br1
& office. ahu in linen closet with r/a in living room furred down
top of br2 closet to serve br2 & living room.

only in certain layouts can houses easily be retrofitted in this manner.
in homes where this can't be done..the other option is foam insulating
the roofline.

best of luck.

[newstudent]

https://www.youtube.com/watch?v=h3vgtxPtvcc

This video shows the main duct work. The other half of the duct work is not shown in the video, because it is on the other side of the cathedral ceiling. Ideally I'd like to get rid of that spider web of supply lines in the attic to only have two very big supply lines. One feeding the length of the cathedral ceiling and the other supply line feeding the length of the hallway beneath it. Making a new header, duct work, etc, will likely cost a couple of thousand. Annual AC cost is estimated at $600, plus heat gains, I might save $150 a year. Kind of a long payoff. But it just annoys me how poorly designed this house's HVAC was built.

http://www.allentate.com/~p2177209p~...st-Subdivision
has pictures of the inside.

That big supply duct you see in the video going into darkness sits right on top of that cathedral ceiling ridge. Pulling it out and putting it inside by lowering the ridge ceiling is easy.
Ignore all my talking about zoning the system in the video, that is no longer under consideration.

It's in North Carolina and it is humid, but not as bad as LA.

[jtrammel]

I really don't think you would save much by moving the duct inside. If you moved all of it and the furnace/coil yes but not just some of the lines. The duct system could be designed much better and wrapped with r8 insulation but the biggest savings will be air sealing the ductwork. Then foaming the roof deck or air sealing the attic floor and better insulating the attic floor and ductwork and adding a radiant barrier to roof deck.

[motoguy128]

New houses should have all duct work in furred down enclosures, IMO. But so often how new homes are designed (really...someone actually designs those things vs. mere "cut and paste" out of a stock plan computer data base?) make it difficult to run duct regardless of whether it's in an attic, basement/crawl space, or even in conditioned space chases (aka furdowns). Fundamentally I believe house design needs to change significantly to return more comfortable, energy efficient structures, but current market trends still favor the McMansion layout, which has shown in my mind to be a world of problems due to the emphasis on appearance vs. functionality.

You're missing something there. McMansions focus is on the layout, features, function and they they pretty up the outside with at least 1 or as many as 3 or 4 fake architectural themes (colonial, victorian greek rivial, georgian, dutch colonial, etc.) by mising and matching fake add-on shutters, dormers, and siding types. The exterior appearance is clearly...to me at least... an afterthought.

I do agree that with all the bazillion codes out there (some of which I think seem quesitonable and make you wonder who is really driving the requirements) it's a glaring oversight that ductwork is left in an unconditioned space on new construction. We could go one step further and set a maximum HVAC equipment size for each zone based on building linear wall size. So you might pick something like 80 linear ft/ton as a ratio. So a 2000sqft home would be limited to 2.5 ton maximum. SO rather than focus on R-values, a contractor needs to add shading, insulation, and building envelope tightness to meet that minimum requirement.

[newstudent]

Instead of foaming the entire roof deck I'm going to ask a contractor to just frame around the HVAC unit with 2x4's and use regular fiberglass batts, to basically make a mini conditioned room around it. Hopefully in a manner that can be taken out easily when the furnace is replaced latter in life. Maybe using 2" foam would work better for that reason.

Obviously the furnace is going to need an air supply for burning, so a new 3' long duct will be needed from the furnace to the outside enclosed wall.

Can this duct be closed off during the summer when the furnance is obviously not running? Obviously if someone forgets to remove it before turning on the heat it will not be good!

I think that is about the best I can do to bring everything into conditioned space short of ripping the old system out and redoing it.

[genduct]

Thoughts on why installers are telling me this is not worthwhile, yet everything I read says it is? Who's right?
Because we are all creatures of HABIT. It is what we always do!!!! To think otherwise would call into question our idea of "best practices"
The main change for the latest Ed of Man J was it's attention to duct energy losses.

2 thoughts first, you need a trunk and branch duct system not that spaghetti system with 2x the surface area AND
I think it would be easier to install some "knee walls" that would more effectively get a good deal of your equipment and duct inside the thermal envelope.
THere is not a lot of leakage with that flex but I think you could see a 1/3 reduction SWAG

[newstudent]

Genduct, thanks for that Spiritual Wisdom and Godliness or was that some wild a** guess? LOL.
A 1/3rd reduction in energy use would be great!

[energy_rater_La]

instead of building a box around equipment, adding make up air for furnace in box,
bringing some ducts into living space and worrying about closing off make up air for
furnace in a box...(which you wouldn't have to worry about in the summer fyi)..
you need to put pen to paper and estimate what ball park costs this would require.

materials, labor, pita factor working in attic, sheetrock finishing for cathedral,
painting..adds up to quite a bit to me and I'm a diy person.(except sheetrock finishing)

then the problem of finding someone to competently do the work.

I'm all for ductwork inside living space. but all of the duct work, all plenums
and all returns. all equipment.
but this isn't your set up.
no common area to feed all ducts to all rooms inside the living space.

say you decide to foam insulate the attic..still you have work to do.
finding a competent installer.
removing insulation in attic at minimum
3" from eaves of house.
moving junk out of attic.
venting bath fans, stove, adding a duct for make up air for furnace
and gas water heater if w/h is in attic.
all prior to the foam install.

granted your duct layout is crap. I think we all agree on that one.
and like Genduct says..flex is less leakage than hard pipe.
I would add that you still have to mastic seal duct take offs at plenum.
plenums to equipment, return air and each supply box where it enters
house & supply grill is attached. flex duct leaks at each end. depending
on the care that was used to cut holes in supply plenum, duct leakage
varies.

so add up costs for foam & venting, make up air & duct sealing.

compare the costs of option 1 (equipment in a box etc) to option
2 (foam etc).

how high are your utility costs now?
have you been in the house a full heating and cooling season?
comfort issues? hot rooms, cold spots..allergies?

I can't say that I'd spend time building box for furnace and furring down
cathedral for one duct.

best of luck.

[newstudent]

Ok thanks for the information. I'll chew on the numbers a bit and see what works out best.

[coolmen]

I agree, Air sealing and insulating in its self will give you great results.Build a insulated room around the equipment in the attic ive seen done before. redesign the whole house is not needed un less your duct were undersized and you have bad static pressure.

I really don't think you would save much by moving the duct inside. If you moved all of it and the furnace/coil yes but not just some of the lines. The duct system could be designed much better and wrapped with r8 insulation but the biggest savings will be air sealing the ductwork. Then foaming the roof deck or air sealing the attic floor and better insulating the attic floor and ductwork and adding a radiant barrier to roof deck.

[newstudent]

Here are some photos of the main trunk being furred down with framing. The left hand side, has a boxy room sticking out. Ontop of that is the old distribution box which will feed the bathroom beneath it, and two 6" flex tubes will continue to the two bedroom closets and exhaust in the actual bedrooms.

I have a general contractor friend that is doing the labor. Material costs are around $1,000. I figgure if I save $30 a month break even will be around 3 years. I did find two ducts in the attic that did not even have a zip tie securing them to the ceiling register, just pressure fit.

If I were to do it again I would of NOT furred down the main cathedral ceiling and just had a huge exposed duct work trunk.
second photo is of hole in bathroom ceiling.
last photo is of furred down bathroom ceiling.