Double Stud Wall Green?

fcarver

My wife and I recently toured a new home in our area that is being advertised as an "Eco" home. It contains all that would be expected with regards to that method, Solar array, solar domestic water, etc. The part of the construction that bothered me was the use of a double stud wall. I do understand the need to reduce thermal bridging. However, as a builder myself, this method seems to use a large amount of lumber, even at 24" o.c. Is there anyone out there who has done a detailed analysis on this? This home had 2x4 doubled 24" oc with 2x10 top and bottom plates. From my experience ICF's seem to be a much more Eco friendly product. Just my 2 cents.

concretemasonry

The wall was green before they cut the trees.

You are right about the ICFs if you look at the real picture. You also get thermal mass, which makes the solar more effective and reduces heating plant sizes.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

mdshunk

Even if it uses a bit more lumber, most of our domestic studding is coming from junk, fast growing trees like Loblolly Pine. Don't worry about a tad more lumber being used. They're planting plenty of that crap.

concretemasonry

Many developed countries place a "green" value on the "junk" trees and encourage improved use of natural resources. - They are now the ones with a larger prespective of green without increasing costs.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

gregj

It is now "green" to use as much lumber as possible. Since every bit of lumber is composed primarily of the greenhouse gas carbon dioxide that has been removed from the atmosphere.

Using the lumber in houses where it will not decompose (hopefully) keeps the carbon dioxide out of the atmosphere. So use as much lumber as possible and reduce global warming.

Red Adobe

lets say 100' of ext wall

rough math
normal on 16" 75 studs
double on 24" 104 studs
2x10 plate instead of 2x4
labors probebly 10% more (mark plates at 1' and stagger)

where its green is insulation space. If i remember correctly the R value is 250% that of just a 2x4 wall

other benefits i can think of are......
stronger walls 12" center basicly and on wider base
Better joist connections
wirring weaved thru meaning less labor to bore holes??
wider window sills for the cat or plants

jmho

K2

I did double stud walls between units in 1985 and still own the building. I'd say it was one of the smarter things I did in 1985. I also cut the plywood subfloor between units. All for sound. Regrets: there is a 1/2 inch space between the 2x4 walls, (top plates) which in case of fire can create a draft . I would do the top plates differently if i was going to do it agian which i probably won't. Actually I think triple isnulation would have been the best for me in my 1985 project instead of double insulation.

mickeyco

I am so tired of all this "Eco" crap, look out the window there are trees all over the place, there is no lumber shortage in this country, adding a couple extra 2 x 4's to a structure that's going to be standing for decades is hardly a waste or harmful to the environment. You want a real "Eco" home, dig a hole in the ground and live in it.


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dougchips

In theory the impact from using the trees is much less over time than the amount of energy that would be needed to heat/cool the structure.

Made up numbers:

Killing an extra 30 trees once is better than

wasting 300 gallons of heating oil every year for the next 150 years (assuming the house lives 150 years, hell some live 200 years +)

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Red Adobe

Excellent point dougchips.

The way its looking it might be a rough winter for alot of people if they arent prepared for the higher costs

sawyerEd

dbl 2x4 walls are sometimes called here STC or Sound Transmission Class walls and are code requirement in urban multi unit housing on walls facing the street. However stopping sound by eliminating mass bridges is very effective in stopping thermal bridging also. STC walls usually use 2x8 plates on staggered 12 in centers and a layers of R 12 applied on each side of the inwall wiring and plumbing. Dont forget that carefull fitting of batts is more important than just stuffing more in.

CatAlii

Just as Red Adobe and dougchips pointed out they are very green if you take into account the energy savings. Green building also means building a sustainable home that is extremely comfortable for its occupants and I think the double stud wall construction helps to meet both of those criteria. It's all about pros and cons.

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Cathy

Michalak Construction / MCC on Facebook / MCC on Twitter / MCC on Google+

MALCO.New.York

I like that!!!!

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builder brian

From an embedded energy stand point utilizing wood is far more sustainable than ICF's. Insulation is probably the single fastest green payback you can do on a house. Photo voltaic and solar thermal can't even come close to the payback of a 2x10 dbl stud wall system. As for "Eco Crap" big GCs here are laying of people in droves and I can't even schedule new projects I have so much work. Beleive it or not but its the future of things to come.

d-rez

A lot of the Pine 2x4s we use are grown on plantations, specifically grown for construction. It's the bigger dimentional lumber that is being cut from forests.

K_Tile

Those builders that wont go green will be losing the "green".

Try this

Larsen Truss

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Kevin Tindall

mickeyco

From what I'm seeing of the Larsen Truss, it won't meet code.





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critter

One thing to think about with the deep fiberglass walls. At 70 degrees and 30 per cent humidity, the dew point of water vapor that enters the walls is around 37 degrees. In these walls, that 37 degrees will certainly occur in the fiberglass near the ice cold OSB sheathing. That means water, water means mold and r-value drop and rot. Walls with a foam exterior will keep the fiberglass area above 40 degrees except in the coldest weather. If you believe that you can keep water vapor out of walls, think again. Drywall primed and painted acrylic one or two coats will admit about a cup of water a year through the wall of a small room. A hole drilled for wiring from the basement - about 50 cups per year. A poorly sealed receptacle is about the same as a hole. You will need to start to think more about how to dry walls out than how to prevent moisture getting in if you want to avoid mold/health issues that are looming on our horizon.

sawyerEd

Critter is right. Almost impossible to get 100% dry walls. But you can get to 90% with a little diligence and provide a drying/breathing mechanism for the other 10%. Technical design will vary in different climates and moisture/energy flow will vary with the seasons. Vapor retardant layers can breathe in both directions if there is some airspace designed into the wood framed wall. Capillary breaks and thermal breaks can be included in the envelope, sometimes using inexpensive materials. Vaulted ceilings and solid masonry present some special problems but even these can be allowed to breathe when conditions are right. Try to understand the problems in each case and take appropriate measures. There is a product or solution for everything.

gregj

I don't understand why a thicker wall would be more prone to this problem than your typical 3 1/2" or 5 1/2 inch wall with fiberglass. In either one the dew point is within the wall so a vapor barrier is needed on the inside.