[Greenbuilding] Insulation, windows, siding...oh my! (Take 2)

[Bob]

Justin,
Where are you located? Local climate has an important bearing on my 
suggestionss/advice.
Lacking that, I'll try to stay generic with caveats (where I remember 
them).
> Anyway, we are looking at redoing the roof & gutters, rebuilding the 
> chimney (from the roof up only), replacing the siding on the house, 
> insulating the walls, replacing the water heater and replacing the 
> windows.  And I am already in the process of replacing/updating the 
> electrical system.  It is a 1950s ranch (1955 I think) with many of 
> these systems probably original to the home.
>
> We have talked with a few roofing contractors to get estimates.  One of 
> them suggested leaving the current roof, putting foam insulation over 
> it, and then reroofing.  We currently have some insulation, rather 
> inadequate though, in the attic area.  Would this double layer lead to 
> problems?  What about having the good insulation layer at the roof level 
> instead of at the ceiling of the living area, just in terms of an 
> efficiency aspect?  I have been thinking that we would have them remove 
> all of the current attic insulation and reapply something new and 
> uniform (foam?  cellulose?).  And while it is exposed it would be a 
> great time to rewire things!  :)
>
>   
There is a good argument for the roofer's suggested option, with a few 
key additions, and it will move the attic into the conditioned space 
(providing he is proposing enough insulation) - whether the framing 
would let you plan to expand into it as occupyable space or just as 
conditioned storage.  It could well be the most cost-effective option as 
well.
A fifties ranch probably still has full rafters but a layer of sheet 
foam under a new deck will add dead load so check the rafter capacity.
The insulation R-value should approximate what you would have put on the 
attic floor; this is a pretty thick layer and may complicate reroofing.  
Consider an outside layer (easy to apply and should cost less per sq. 
ft. and R-value) and having another layer spray-applied to the underside 
of the deck.  They cold spray the critical bridge area of the perimeter 
and from the top plate to the deck, completing the insulation envelope 
with the walls. 

The existing insulation in the attic can be left in place or removed for 
reuse elsewhere, depending on type, material and condition.  Most 
original '50's vintage attic insulations I've seen were thin and pretty 
deteriorated.  If it is loose or batt Rockwool® (gray fibrous and 
friable material that often looks like dirty white fiberglass or 
cellulose) is good insulation but can be mean to handle.  I get a more 
persitent and painful itch from it and wouldn't consider doing anything 
without a good respirator, gloves and goggles, and a disposable coverall.

 When calculating the option of re-insulating the attic floor, be sure 
to allow (a lot of) time and materials to find and seal /_all_/ of the 
openings / penetrations through the ceiling plane.  This will include 
the plumbing wall, any dropped soffets, any wiring (top plates and 
ceiling electrical boxes or other plumbing penetrations, exhaust vent 
(duct them to the exterior and insulate the duct if you go this way) and 
the space around a chimney (if any), and flues if not.

> For the wall insulation we currently have zero.  These are 2x4 stud 
> walls, 16" OC.  Exterior wall sheathing is an odd version of particle 
> board, it appears:  It is rather coarse material that isn't very dense 
> nor glued or pressed together very strongly.  Then there is a paper 
> layer of some sort.  Most of the weather-shell is shingle.  But there 
> are areas of the front that are brick about half way up, then topped 
> with T-111 type paneling.  It is an odd mish-mash.
>   
Eliminate the brick 1/2 cladding!  I have seen far too many 
moisture/mold problems that traced back to mortar squeeze bridging to 
the subsiding, allow ing moisture to wick into it from the brick.  The 
brick is nearly transparent to water; there is supposed to be an air gap 
and weep gaps in the bottom brick course to let it drain back out but 
the system doesn't work that well in the real world.  The paper layer, 
probably either rosin paper or tar paper, served to deflect that water 
and to provide a pretty good air barrier, even if that was not the 
original intent.  The subsiding may be an asphalt impregnated version of 
Cellotex® or something similar.  I don't see it much these days except 
as an alternate foundation-to-sill sealer, probably because of it's low 
structural strength.  You probably can't salvage it or the shingles for 
re-use without really boosting demolition costs because whoever did it 
would have to be careful - not usually compatible concepts.

> Anyway, I mention all of that because my thought is to remove the siding 
> and sheathing, do some rewiring while it is exposed, then do some 
> insulating, replace the sheathing (perhaps use new stuff?), and put up 
> new siding.  (The current shingles are all rather warped at the vertical 
> edges, and I question their effectiveness.)  If we did it this way I 
> have been thinking I would use some expanding foam insulation in the 
> walls:  firstly, to achieve good insulating values, secondly to provide 
> for air sealing.  (Our house is rather permeable.)  But I realize that 
> isn't the greenest material out there.  Also, now that I am exposing the 
> stud bays, would it make sense to go around and in some manner add on 
> some more studs to achieve a deeper bay?  And what to use for siding?  
> Certainly not vinyl, but what about hardi-board type materials?
>
>   
Your idea makes sense to me.  However, unless your climate is 
particularly wet/windy such as Pacific Coastal or has high outside 
humidity, I think I'd consider damp-spray cellulose with a continuous 
layer of insulation (usually foam board) to decouple the framing and 
covered with an air barrier as the best performance for dollar.  I don't 
mean to knock spray foam but in this area it is more expensive.  Both 
will go a long way to blocking air leakage.  A housewrap may not be 
essential to block air but I consider it more valuable as a drainage 
plain.  It is essential if you rebuild the half brick for appearance, in 
fact Joe Lstiburek makes a very good case for double layering it under 
the brick.  I don't think that adding stud depth will prove 
cost-effective; I'd use a thicker (higher R-value) continuous insulation 
instead.

> have also thought to insulate under the floor, again with expanding foam for air sealing purposes (not so much for insulation value, but 
> just to seal the house from the crawl space).  We have had a few 
> interesting experiences with things go wrong in our crawl space, and 
> that has lead us to realize how much air penetration we get through the 
> floor.  It is just 2x10 sub floor (on top of the joists) with about 1/2" 
> gap between each board, and then the wood finish flooring of the house.
>
>   
Consider converting the crawlspace to conditioned space as well.  
Insulate the perimeter, leaving a couple inches of exposed perimeter as 
a termite inspection gap.  Seal shut and insulate any vents (if you need 
to ventilate, do it with a fan you can tune to needs and control, the 
vents do not work as intended).  Install a sealed "bathtub" vapor 
barrier with sealed seams and sealed to the perimeter and any piers or 
support walls.  Again, it is likely to be most cost-effective and should 
give better performance.
> Windows:  I have read many a thread here about windows.  I don't like 
> vinyl myself (vinyl is evil!), but it can also be so much cheaper...  :(
> We have 11 windows in total, if I count correctly.  A number of those 
> are odd sizes, though, and to the larger end of things.  Our current 
> windows are all aluminum, double pane.  They are cold and sweat a lot 
> during the winter.  The ones in the bedrooms are all rather short 
> (perhaps only 3' high?), high (bottom of window is about 4' from the 
> floor), and more normal sized.  There is one large one in the living 
> room, perhaps 5' high x 8' wide?
>
>   
Regardless of what window option you choose, get the EEBA pamphlet on 
proper flashing.  I believe it is "Moisture Control"; it's worth every 
penny of the very low cost as insurance against water damage at this 
critical, leak prone area in the future.  You are planning enough work 
that will provide access to do it right that I consider it suicidally 
foolish not to.
> We were thinking of just getting a high efficiency electric water heater 
> as a replacement (current one is electric, too).
>
>   
Is this a ducted heat system?  What's the condition/ location of the 
ducts and furnace.  If you are planning a new water heater, how about 
considering an integrated heating/hot water system?  It uses a slightly 
oversized, high efficiency water heater to provide domestic water _and_ 
hot water to a hydronic heat exchanger in the air handler housing (like 
a small boiler) to heat the airflow.  They are very effective, more so 
in tight, high efficiency buildings - which is what you are proposing.
> And on top of all of this the daughter wants to go to college this fall, 
> so budget is a big concern!  I would love to be able to do things right, 
> but that is usually the more expensive route, too.
>
>   
If you can't do it all at one time, make a long term plan, prioritize 
the shell measures on what most needs immediate repair (that sounds like 
the roof) and just don't do anything as an interim measure that will 
have to be undone (or precludes) a later stage measure.  If that isn't 
complicated enough, allow flexibility for new technologies or current 
ones that may cost less in the future (PV pops to mind).
> Whew!  Thanks for all your advice.
>
> --  Justin
>
>   
Whew!  Forgive the excess.  I'm decompressing from a hard week; this let 
me play hookey for a few minutes.
Bob Klahn
YS Building Science

>
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