Hello All,

This is my first post on this forum so go easy on me.  In the process of building (with a builder) our first home in Southeast WI and have some insulation/air sealing questions.  The house is underway and so far the foundation is done and they are in the process of framing with the first floor framing almost complete.  We are doing a pretty standard insulation/construction scheme which I have described below. 

- 3000sqft 2 story colonial
- 2x6 construction with 1/2" OSB sheathing in required bracing areas and 1/2" Atlas R3 Rboard sheathing everywhere else on exterior
- Tyvek house wrap which will be covered by hardieplank or stone
- R19 batts in exterior walls
- R42 blowin in attic
- 2" R10 on 9' high 10" wide basement walls
- Polyvapor barrier on all interior side of exterior walls, under basement slab, between ceiling and attic
- Foam insulation in box sills

So here are a few questions I have.

1) I am considering adding Foamular 250 polystyrene insulation under the basement slab.  Not planning on doing radiant heating but do plan on eventually finshing 2/3's of the basement.  Cost would range from $600 for 3/4" to $1200 for 2" for me to add it myself.  Is it worth doing this?  If so, should the joints be taped.

2) I am considering doing additional air sealing between all the joints on the inside of the cavaties where the studs meet the sheeting.  Is this overkill or does is make sense to do that?  If I do it, what is the best method to do it for a DIYer?  There are some nice systems out there like Knauf & Owens Corning but that is not available to me.  Could I just use something like Great Stuff or Great Stuff Pro for this?  If so, which type of Great Stuff (i.e., Gaps/Cracks vs Window/Door)?  I would probably need a lot of cans but guessing I could still do it for less than $100.  Open to other suggestions as well that would be avaialble for a DIYer.

3) For the garage, it is 2x4 construction and it will be insulated and drywalled and I plan on installing a gas garage heater to keep it in the 50-60F range in the frigid winters.  Currently, there is nothing spec'd under the garage floor other than stone.  Should a polyvapor barrier be added under the garage floor?  Also, would it make sense to add any insulation under the garage floor like the Foamular 250?

Thanks in advance for your wisdom and knowledge.

Someone should chime in to answer your other questions but being that you are in Wisconsin, I would REALLY reconsider R-19 fiberglass batts. They don't perform in real world climate and wood home like yours as R-19 batts, in real world trials, they will perform as R-13 batts. You will pay dearly with heating bills in a Wisconsin winter with an R-13 wall.

I recommend going the route of blown-in cellulose or better yet, open spray foam insulation. You will make the home more air tight, help with thermal bridging, and get a real R-Value closer to R-20 with a 2x6 wall.

Is that insulation you describe really code-minimum there in Wisconsin?

Did you (or anyone else) do any investigation into how much heat and money you could save by improving your insulation?

2) I found it better to use a flexible caulk where I was sealing something thin or narrow like where the studs meet the sheeting or the edges of studs. Foam gets used up too fast on those areas. Save the foam for the deeper or wider cracks.

3) is your garage a slab foundation?

Additional foam board insulation on the outside so you get at least 1.5 inches, seams staggered and taped. This will make any insulation inside the walls work at its rated efficiency by solving the bridging problem, and is also the recommended depth for condensation prevention.

Windowpane caulking on the inside of the walls every place sheathing meets framing. If you go the caulk route, get yourself a battery powered caulk gun - it will be worth every penny you spend on it. You will have to make sure whatever caulk you use is compatible with your R3 Rboard sheathing. Use polurethane caulk where you can. If you prefer foam, using great stuff will cost you lots more than $100, and it is fairly miserable to work with, doesn't stick well, slumps etc - but they do make small DIY foam kits of better foam that will do the job.

To get the fiberglass batts to work the insulation installation job needs to be perfect, and you should use the high density R21. If you get more foam on the outside, and do the windowpane caulking, you can use fiberglass batts, but blown in cellulose would probably be better and not much more in cost.

2 inches of foam under the basement slab but 4 would be better. If you can find used foam it would save you lots of money and as it is going under the concrete it does not matter how pieced together it is. Yes tape the joints.

Be careful with that polyvinyl - definitely under slab but probably not a good idea on walls or in ceiling because of condensation issues. You need to have a way for the walls to dry.

As long as you have room for it and the ceiling will support the load, get R50 or better in the ceiling. Blown in cellulose is pretty inexpensive, so while you are doing it you might as well get as much as you can in - even up to R70.

-Rosalinda

Thank you all for the great feedback.  I had a feeling I would get an earfull on what we currently have spec'd out as I realize that it is not ideal.

WI's Energy Conservation code (SPS 322) requires minimum R19 in the walls and R38 in the ceiling.  We are doing a 3rd party energy certifiction through the WI Focus on Energy New Homes Program.  I will ask the consultant to do an analysis with different types of wall insualtion and ceiling insulation and then check with the insulation contractor for the cost and calculate the payback time.  I understand and appreciate that there are a lot of improvements we could do to what we currently have spec'd out but obviously cost is the biggest factor, especially since the contract/loan have been done for a while now and everytyhing we do at this point is coming directly out of pocket.

I am trying to see if there is something I can do that will give a big bang for the buck and everything I read points to air sealing as a place to start which is why I thought about taking on that challenge myself.  Additionally, the insulation under the basement slab and garage slabs was another place I thought about the cost of those are pretty high and I am guessing the payback on these would probably outlive our stay in this house which is possibly 10-15 years.

Regarding the polyvapor barrier on the walls/ceiling, there seems to be a pretty big debate on this issue which leaves me confused.

I am guessing the payback on these would probably outlive our stay in this house which is possibly 10-15 years.

In Green Building, we want to build a place that saves energy over the life of the building, not for just the period we own it, however short.

I would be surprised if the underslab insulation didn't pay it's way in Wisconsin, even over the shorter haul as you would like to heat the garage with a separate heater.

You're correct that air sealing is good bang for the buck. Doesn't the contractor have to pass a blower door test?

Nick,

Prescriptive code minimum is r49 for ceilings in both zones of WI, although ResCheck allows deductions if you beef up other areas which may have happened in your case.

Buy yourself a foam gun and the cans of foam that screw on, you get much better yield out of those cans and the cost of the gun will be worth it for that, plus ease of use, control, using overhead and control of the bead size. Tubes of caulk will only get you about 30 LF, and if you want to do every bay that adds up to an enormous amount of sealant.

Look into BIBS for walls and cellulose for attic, it performs well here. I am a Focus on Energy Home Performance with Energy Star installing ally in WI, you can PM any other questions you may have and I can help you answer them as I have time.

I have a hard time with the idea of cutting back on energy saving measures because it won't compute over the 15 years you will be in the house; ie: "cost effectiveness" although I realize its a necessary part of building. So when you have your consultant do the report, make sure he incorporates a realistic increase in the cost of energy over the next 15 years. In terms of the basement slab, also factor in the "cost" of comfort - maybe it won't compute exactly, but there is some intrinsic value in not having a cold, damp basement floor. I wouldn't bother with it in the garage. Don't forget foaming around the windows and doors.

If you can have a blower door test done prior to insulation, you'll be able to address your infiltration; otherwise its a crapshoot.

Posted By Bob I on 28 Feb 2012 10:59 AM
I have a hard time with the idea of cutting back on energy saving measures because it won't compute over the 15 years you will be in the house; ie: "cost effectiveness" although I realize its a necessary part of building.

Unfortunately this is a major sticking point in energy builds. When it can cost $100k+ more in construction costs to do a "energy build", this is a cost the homeowner will never, ever see in their lifetime. In the end, money talks and most people will go the route where it costs less money. Those who have deep pockets can have bragging rights when they build a very efficient home but they have deep pockets so spending more money on their home is not impacting them financially.

When people spent $40K on a photovoltaic setup, it would take 30-40 years to break even. That is not even counting the upkeep costs to keep the PV setup running, replacing solar panels, updates, etc.

Until these energy saving measures come down in price, they are just banter for 80% of the population. When it is coming down to feeding your family and caring for their health needs, these energy discussions will always take a back seat.

I would strongly, strongly recommend spray foam in the walls. As has been mentioned you won't get the full rating with bats for a lot of reasons. The sealing effect of the spray foam is worth it alone. We have 2+ inches of foam and then bats behind that in a 2x6 exterior wall.

If you plan to heat the garage insulate under it, if you don't plan to not heat it, don't. Our garage slab is not insulated, but the 2x6 walls are standard bats (wish I had foamed them) and the ceiling is R30. The garage never goes below freezing in winter because the ground is warmest part of the garage, I believe if we had insulated it would get below freezing. We do have 2 inch all the way around the footings outside as well as the house.

Posted By Brock on 28 Feb 2012 05:57 PM
I would strongly, strongly recommend spray foam in the walls. As has been mentioned you won't get the full rating with bats for a lot of reasons. The sealing effect of the spray foam is worth it alone. We have 2+ inches of foam and then bats behind that in a 2x6 exterior wall.

If you plan to heat the garage insulate under it, if you don't plan to not heat it, don't. Our garage slab is not insulated, but the 2x6 walls are standard bats (wish I had foamed them) and the ceiling is R30. The garage never goes below freezing in winter because the ground is warmest part of the garage, I believe if we had insulated it would get below freezing. We do have 2 inch all the way around the footings outside as well as the house.

Great advice. In my current leaky "tract home", which has R-13 batts, the home leaks air like a politician.

A couple of days ago there was a fire about 3 miles away. We had all the windows closed and the smoke poured into our home and by 4AM it woke me up. The home leaks so bad that outside air is constantly finding its way in.

Lbear,

It almost sounds like your home has negative pressure.  If so, then be careful about gas appliances backdrafting.  I would think that a house with positive pressure would keep out the smoke.

Posted By greentree on 27 Feb 2012 08:56 AM
Nick,

Prescriptive code minimum is r49 for ceilings in both zones of WI, although ResCheck allows deductions if you beef up other areas which may have happened in your case.

Unless I am reading the code wrong it says: "Comm 22.32 Specific insulation requirements. (1) CEILINGS WITH ATTIC SPACES. R−38 will satisfy the ceiling R−value requirement for a dwelling where the full height of uncompressed R−38 insulation extends over the wall top plate at the eaves."

Posted By ICFHybrid on 27 Feb 2012 07:50 AM

I am guessing the payback on these would probably outlive our stay in this house which is possibly 10-15 years.

In Green Building, we want to build a place that saves energy over the life of the building, not for just the period we own it, however short.

I would be surprised if the underslab insulation didn't pay it's way in Wisconsin, even over the shorter haul as you would like to heat the garage with a separate heater.

You're correct that air sealing is good bang for the buck. Doesn't the contractor have to pass a blower door test?

I understand all the recommendations of spray foam instead of batts but that reality is that is not going to happen as it will be thousands more and we are already stretched on the budget. I have to agree a bit with Lbear that for a person building a house like myself. You find that every way you turn, someone is trying to sell you something energy related, whether it is insulation, windows, HVAC, etc. That is obviously the hot topic in home building and although it may appear to be "green" it is not always the most economical to do and the only "green" thing about some of it is what ends up in peoples pockets. Anyway, off fuzzy stuff and back to the topic. I did find out from the energy consultant that the blower door limit they are shooting for for my house is 1587cfm with the design of the house as shown above and doing nothing else like the things I suggested. So, my question to the esteemed experts of this forum is, how much would you expect this number to go down if I did the air sealing as I described above by foam sealing all the joints between the studs and the walls and all the windows and any other crevices? 5%, 10%, 20% improvement?

Nick,
22.32 (1) was written for attic trusses 2x12 lower chord. Read 22.32 (2)

Posted By Nick_M on 28 Feb 2012 09:09 PM

Posted By greentree on 27 Feb 2012 08:56 AM
Nick,

Prescriptive code minimum is r49 for ceilings in both zones of WI, although ResCheck allows deductions if you beef up other areas which may have happened in your case.

Unless I am reading the code wrong it says: "Comm 22.32 Specific insulation requirements. (1) CEILINGS WITH ATTIC SPACES. R−38 will satisfy the ceiling R−value requirement for a dwelling where the full height of uncompressed R−38 insulation extends over the wall top plate at the eaves."

Posted By ICFHybrid on 27 Feb 2012 07:50 AM

I am guessing the payback on these would probably outlive our stay in this house which is possibly 10-15 years.

In Green Building, we want to build a place that saves energy over the life of the building, not for just the period we own it, however short.

I would be surprised if the underslab insulation didn't pay it's way in Wisconsin, even over the shorter haul as you would like to heat the garage with a separate heater.

You're correct that air sealing is good bang for the buck. Doesn't the contractor have to pass a blower door test?

I understand all the recommendations of spray foam instead of batts but that reality is that is not going to happen as it will be thousands more and we are already stretched on the budget. I have to agree a bit with Lbear that for a person building a house like myself. You find that every way you turn, someone is trying to sell you something energy related, whether it is insulation, windows, HVAC, etc. That is obviously the hot topic in home building and although it may appear to be "green" it is not always the most economical to do and the only "green" thing about some of it is what ends up in peoples pockets. Anyway, off fuzzy stuff and back to the topic. I did find out from the energy consultant that the blower door limit they are shooting for for my house is 1587cfm with the design of the house as shown above and doing nothing else like the things I suggested. So, my question to the esteemed experts of this forum is, how much would you expect this number to go down if I did the air sealing as I described above by foam sealing all the joints between the studs and the walls and all the windows and any other crevices? 5%, 10%, 20% improvement?

Based on your 2 posts and never seeing your house plan or noting window and door quality that you should get down to 1000 CFM +/- 587 CFM, that's ballpark assuming you do the work.

Maybe its to late to consider but nobody mentioned thermal brigding and placing rigid insulation on the outside. Are you using energy heel trusses to get more insualtion in the attic. NEVER use batt insualtion, 40% of cavities are not the standard 16/24 inch on center. To hard to get a good fit. Blown.sprayed insualtion will fill the voids.

Why should you go above code minimum insualtion and air sealing?
Lower utility bills
Increased durablity- lower maintenance
Comfort- how do you price that
Increased home value.
Healthier home with better indoor air quality
INFLATION- it will make the investment worth that much more.

I think we look to much at payback as the only or driving criteria. Lower utility bills are only part of the benefit.

When you build right the home is more durable. Components last longer, you dont get unexpected surprises like mold, you paint less, etc. Hard to put an exact price but worth something and probably a lot

Comfort - when the mean radiant temp of the wals is warmer in the winter and cooler in the summer the occupants are more comfirtable. When there are no drafts there is increaed comfort. How much is that worth.

Todays minimum code will be tomorrows substandard housing. Homes that are better insulated will sell for more in the full. Add this to the so called pay back.

You cant control your air quality is in leaky home. You can escape from air borne allergens. Plus leaky homes are more prone to mold. The home will be less dusty.

Inflation- What do you think will happen with inflation given the administraion deficit spending. You can lock in your cost and low mortgage rates and pay the investment back with inflated dollars. Energy prices will be higher too.

It is always cheaper to do the improvements atthe design/construction phase rather than trying to retorfit.


Here is some light reading that may help you.

http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones

"When it can cost $100k+ more in construction costs"
I'm not sure where LBear comes from but I don't think anyone on this forum is thinking that it should cost $100K more for the energy measures we're talking about. Could be true if you're building a million dollar home, but nowhere near that ballpark for a normal house. Sounds like someone trying to justify building a 1970's style house (2x6 walls with fiberglass). R-19 was designed in the days of $.25 per gallon gasoline. If, in these days of $4. gasoline you want to build a fuel hog, go right ahead. Good luck selling it in twenty years.

Posted By Nick_M on 28 Feb 2012 09:09 PM

I understand all the recommendations of spray foam instead of batts but that reality is that is not going to happen as it will be thousands more and we are already stretched on the budget. I have to agree a bit with Lbear that for a person building a house like myself. You find that every way you turn, someone is trying to sell you something energy related, whether it is insulation, windows, HVAC, etc. That is obviously the hot topic in home building and although it may appear to be "green" it is not always the most economical to do and the only "green" thing about some of it is what ends up in peoples pockets. Anyway, off fuzzy stuff and back to the topic. I did find out from the energy consultant that the blower door limit they are shooting for for my house is 1587cfm with the design of the house as shown above and doing nothing else like the things I suggested. So, my question to the esteemed experts of this forum is, how much would you expect this number to go down if I did the air sealing as I described above by foam sealing all the joints between the studs and the walls and all the windows and any other crevices? 5%, 10%, 20% improvement?

The value proposition:

Use blown insulation in the cavites (not batts), and save the foam budget for the exterior, where you get the full-R of the foam, not undercut by the thermal bridging of the framing.  The cost-adder of going with wet-sprayed cellulose vs. low density batts isn't huge, but the air-retardency (and R-value stability at high temperature differences) of the cellulose is FAR better.  New-school superfine fiberglass (Optima or Spider) at 1.8lbs density or higher is similar to cellulose, and it adds ~ R1-1.5 to the whole-wall R value, but it's usually more expensive than cellulose.

Detail the structural sheathing as the primary air-barrier- caulk under the stud plate with acoustic sealant, as well as where the studs & plates meet the sheathing.  Either primer & tape (with housewrap tape) the seams of the sheathing, or glue the sheathing to the studs at the edges with construction adhesive as it goes up and apply duct-mastic to the seam on the exterior.

Use enough exterior foam (or high density rock wool panels, which offer far better drying capacity to the exterior) to protect the sheathing from wintertime condensation pf interior moisture drives, and skip the interior poly. In WI R3 doesn't cut it anywhere, even on  2x4 construction.  Most of WI is in US climate zone 6 , where with 2x4 construction you're looking at R7.5 min for the exterior insulation, R11.25 for 2x6 construction.   With R13 in rigid foam (2" of iso) + a cellulose filled 2x6 studwall with a 20% framing fraction  you're looking at a total  whole-wall R of ~R27 for less money that what it would cost to do 5" of closed cell cavity fill (R30 center cavity) in 2x6 construction that delivers a whole wall R of ~ R17 or so.   Staggering the seams of the exterior foam with the seams of the sheathing by a foot or so and sealing the seams of the foam, as well as the edges.

If the 2" of foam on a 2x6 framing package is still too rich for you, consider the relative costs of backing off the framing package to 2x4s and going with R13 exterior foam instead of the IRC min of R7.5.  The difference in whole-wall R between 2x6 and 2x4 construction is only ~R4.  With 2x4 & cellulose + R13 exterior foam you're at a whole-wall R of ~R23, with a total wall thickness comparable to a 2x6-no-foam stackup.

The fractional improvement of any air sealing measures depends entirely on where the air is actually leaking, and that's not at all  no-brainer to be answered on a web forum, and can only be figured out on-site during testing.  It could be a 1% improvement or it could be a 50% improvement.  But you'll never get to under 2ACH/50 without a plan and an air-sealing Tsar chasing it during construction.  It starts by defining the primary air barrier that extends from the sub-slab poly all the way to the roof, and monitoring  & checking the critical details at every transition, THEN remediation during blower door testing once the shell is up and presumed gas-tight.

Posted By Bob I on 29 Feb 2012 08:02 AM
"When it can cost $100k+ more in construction costs"
I'm not sure where LBear comes from but I don't think anyone on this forum is thinking that it should cost $100K more for the energy measures we're talking about. Could be true if you're building a million dollar home, but nowhere near that ballpark for a normal house. Sounds like someone trying to justify building a 1970's style house (2x6 walls with fiberglass). R-19 was designed in the days of $.25 per gallon gasoline. If, in these days of $4. gasoline you want to build a fuel hog, go right ahead. Good luck selling it in twenty years.

What I am saying is that when you actually ask homeowners with net zero or LEED homes, what they ACTUALLY PAID for all the "green" energy add-ons, it can EASILY approach the $100K range. When you have geothermal setups, PV's, high-performing windows, etc., you can EASILY get into the $100K range.

Going green is not cheap. Of course there are less costly alternatives to building a good energy efficient home but it's like the PV industry, they are going bankrupt here in the USA everyday. When PV setups cost so much that it take 30+ years to break even for a homeowner, ROI like that will spell disaster for such companies.

Here is the reality on energy efficiency and resale value of a home that is not new (i.e., >10years old). Home buyers don't care! In 15 years when we sell the house, no one will ask what insulation is between my walls or the U value of my windows. They will want to know if the layout, size and what's in the house is to their liking. I know this because my wife is a Realtor and this is what people want to know. She has never had anyone ask her about insulation type or R value and how the home was air sealed or U value of windows and most homeownerse would proably not even know those answers. Thus, for me and most people building a home on a budget, it truly does come down to ROI with a small level of deviation for comfort.

I do really appreciate the suggestions people are making. Unfortunatly, many of them are either too late to do (house is being framed with sheathing and Tyvek already added to exterior walls) or the cost adder of the suggestion is way beyond our budget. I will still be looking at the possibility of doing a blown in type insulation in the walls and maybe upping the attic from R42 to R50.

Sorry to change topics a bit but, ironically, we have another important decision to make that hits ROI vs comfort issue again. The energy consultant is saying that we either need a bath fan to run continuously at 80cfm or I need to add a HRV or ERV in order to get more fresh air in the house. My guess is that I will never see the ROI on the HRV/ERV in 10-15 years living there in comparison to continuous run bath fan. But then I have to weigh the comfort of having a bath fan run continuously, even if it is a super quiet one. Feel free to chime in on this one.