Fiberglass batts used as wall insulation lose about one third their rated R Value.

If it's feasible at this point in your build, you could use XPS for sheathing on the exterior, then use fg in the walls.

Extruded polystyrene, as in these condo townhouses, is often used instead of OSB, plywood or gypsum based materials for exterior sheathing

Here is a link that might be useful: Fiberglass

I've always liked Worthy's XPS solution, but from your post, I think you'd be putting it on top of your sheathing, not just as the sheathing. So instead of the XPS just costing a little more than the OSB sheathing, your spending even more. I don't think that's going to save you money. Go with the dense pack and try to save money elsewhere, like waiting on some landscaping or a deck.

But what I really wanted to remind you of, is that if you do put the XPS on the outside of the sheathing, your windows might need extension jambs, doors too. With 2x6 walls, you're already at the max for most window and door companies. Just keep that in mind as you make your decisions.

Insulation is the one element in your house that can actually save money so it is a poor place to cut costs unless you think the cost of energy will eventually go down. I would stick with the dense pack cellulose.

ok - I will try to make the cellulose insulation make it into the budget. I am a believer - just trying to trim costs.

Let me ask an other question on cellulose. Has anyone every opened up walls after say 10-20 years. how was the integrity of the product? did it shrink/dry/settle etc?

thanks

If you have a knauf installer in your area, you might consider blown in fiberglass. It's what we went with in our wall cavaties. I was skeptical about settling until i had to open up a stud space for some electrical changes and am amazed at how dense packed it is and how much product came out of the stud bay. The netting/mesh material is stapled about every 1/2" so that tells you there is a tremndous amount of pressure there to pack it in. We are impressed with it.

Here is a link that might be useful: knauf blown in

Since you and the builder are taking the time to address air infiltration before hand, and since we're talking 2x6 walls... you're in good shape to start with. There is "high performance" fiberglass that will give you R-21. The product Sierraeast is referencing is known as "blown-in blanket" around here. Cellulose is a good option, too.

still do the air sealing of sole plates, windows, doors,
and use an air tight drywall approach.
tape sheetrock at walls to ceilings even if
installing ceiling moldings.

best of luck with your build.

ok - so not to sound like a penny pincher - I want to open this one up again. My cellulose quote is 2.5 times more $$ than my fiber glass. My fiberglass guy is very highly rated. Uses High density in the walls ( R 21) R 38 in the ceilings.

So - How long would this payback take - if Every, Or is it more a comfort that I would be paying for?

Also - let me ask - Could I do a DIY blown in Cellulose underneath Bats in my attic ( Yes - I would fur out to make it a little deeper) - Or can I just buy bags of the stuff and pack it in the joists?

I am sorry if this sounds like a wrong approach, however i am just not seeing value in teh cellulose job. Am i Missing something?

Blown cellulose should be equal to, or cheaper, (and better) than batts in the attic. Personally, I believe that the Pink Panther should not be allowed in attics, but thats just my opinion.

Its the stabilized cellulose for the sidewalls that costs you the extra jingle.

I dont know where your build is located, but if it were mine,( and I am qualified to do this type of work) I would use the high density batts in the walls, blow the attic myself with cellulose and use the air tight drywall system, like energy rater suggested.

I don't believe there is a functional difference between R-21 of one and R-21 of the other. A basic key here is that the housewrap is properly installed and taped and that all penetrations are foamed.

Rollie - thats the direction that i am heading, and my builder is willing to work with me on this.. thanks for the vote

Two more question - Is there any difference with the cellulose that the insulation guy will do (Nu wool I think) Vs. what i can get at a DIY store and do myself (for the Attic only)

Second - Can i buy the low expansion spray foam in build myself - or have i to by a bunch of the small cans in the Home depot?

thanks all

My guess, is that there is not any difference, or negligible at best. It should be about R3.5 per inch for loose fill/blown in cellulose insulation, and no, you cannot simply just take a bag up there and spread it around lol.

Make sure your attic wind stops are installed properly, also.

You need to install by the "bags per sq foot" rating based on your R values needs, not on the installed inches. If it says you need 190 bags to get R38 over X amount of sq feet, then install 190 bags. Dont simply go by the depth at the time of the install.

There are 2 part spray foam "froth packs" available to the public, but they are expensive, and typically not needed for a DIY with the exception of the rim joist area, where they do a great job of both insulation and air barrier.

Can you give me some idea of your climate zone? are you heating or cooling climate?

If you plan on doing the incidental foam work that is needed, then I suggest a Pagerus (or equal) foam gun (hand held) and a case of cannisters of foam. Zero or low expansion for windows and doors, electrical boxes and other miscellaneous places that need sealing.

If you want to foam behind the electrical boxes in the outside wall, then you can use some of the expanding foam that they sell at any hardware store o one of the big box stores.

Has anyone ever heard of, or used tiger foam DIY or Foam Power DIY?

I have been reading about them and they appear pretty good for a DIY

thanks

Rollie's suggestion of high-density batts in the wall and blown cellulose in a vented attic is the most common combination I see around here.

My next project calls for an unvented attic with ccf under the roof sheathing. Also, sheathing above grade walls in XPS; ccf on the rims, garage ceiling and possibly basement on the interior, followed by fg batts.

doogan.

Those 2 part froth packs are a good product, but they are expensive. The tiger foam is $335 for 200 board feet. (1"x10'x20'). Plus, shipping is atrocious for it, like nearing $100 for freight per container.

While it does a tremendous job, there are more than one way to skin a .... well, you know.

I dont know exactly where you were planning on using it at, but I would guess it would be the rim joist area. If so, this can be done with XPS products much cheaper. The key is to get it in place before the obstacles arive. by obstacles, I mean ductwork, plumbing , water lines, electrical lines etc.

We typically install this before the decking goes down, if there is time, if not, its done as pickup work shortly after.

Worthy,

Not much room left for insulation in the front of that apartment complex! Windows, doors, stacked studs, corners, etc. I think I can see metal bracing in the left sidewall. How do you get any kind of permanent bracing in the front of the building. It looks very dependent on the diaphragm action of the flooring system to me.

Hi Rollie - thanks for the followup

I am in NY state - about 1 hr north of manhatten. about 1100-1500 Cooling days, 5-5500 heating days

I was thinking of using about 1 inch of DIY foam and then letting my Fiber Glass insulator guy install batts. If thats over kill, then I would seal all joints and do the rim with Foam.

I am also thinking if Foam is too $$, to just go with foam board and cut it to fit and maybe just use much less DIY foam to seal and hold in place.

I am trying to find the right balance of cost and efficiency

last question - I was researching some of the DIY products out there and many of them seem to be just a front for selling the same product. 3 web sites ( foampower.com, fomofoam.com and energyefficientsolutions.com) all seem to sell a product called handifoam. does anyoneanyone have any insight into this?

thanks all

Thanks

rollie asked: How do you get any kind of permanent bracing in the front of the building(?)

I noticed that too. This is not my project. When I've used XPS, the engineer had me block the walls all around at the mid-point.

doogan.

While I realy, really like what foam does for airtightness and rigidity of a structure, (especially, if you dont have the knowledge to make the structure airtight without spray foam), its hard for me to justify the costs associated with sprays, especially, since I have the knowledge to do so without.

I have been using the air tight drywall approach since the early eighties, and have documented ach/hr in the .25 range at 50 pa. pressure. While this is certainly not the standard for conventional framed houses, it just shows that with proper knowledge and fortitude, that a near airtight structure can be achieved in conventional platform framed structures.

You are in a heating climate at 5500 degree days, somewhat warmer than me at 7700 heating, and 670 cooling.

Your air barrier should be on the warm side of the insulation. Dont confuse an air barrier with a weather barrier.

An air barrier (in conventionally framed structures) in a heating climate is achieved by either using a sealed polyethylene (some call this a vapor barrier or vapor retarder, which it does also) approach or the airtight drywall approach,ADA which is a series of gaskets that seal your drywall to the framing in very specific locations. Both applications are on the warm side of the insulation.

Too many ppl in a heating climate worry about sealing all the cracks and stuff in the exterior sheathing, thinking that they are sealing up the house by doing so. In effect, they are stopping the breathability of the stud cavity, which in a heating climate, should be allowed to breathe slightly to get rid of any moisture that accumulates in said stud cavity by vapor diffusion or moisture carried into the stud cavity by air leakage, pressure differential, or stack effect.

In a cooling climate, or a neutral heating/cooling climate, then the air barrier moves to the exterior of the wall assembly.

Keep in mind, that having an opening in the sheathing, doesnt make for a leak in the exterior, provided that the weather resistant barrier (which is typically a breathable membrane) and finished cladding is properly in place.

I have done all kinds of wall cavities, double wall, Alaskandinavian strapped walls, quasi foam systems, (foam and lose fill) full foam systems Icynene, etc. All will work and work well, its just the time and money to put them together (properly) doesnt really give you any better product than a well insulated wall assembly with a dedicated, sealed air barrier,such as the sealed poly approach or ADA.

Everyone is tightening their belts under these economic conditions. If you can save some jingle, and end up with a equivalent product, I say go for it.

If I was going to use sheets of rigid foam, I would invert the application you suggested, and put the fiberglass in first, and the rigid over the top, just under the drywall. While I have never done a wall like this, I know that if I were going to, that is the way I would approach it. I think you would have a better barrier for vapor diffusion and a warmer house, but, that is just my opinion, I have no technical data to back it up.

Here is a link to a house I did documentation from start to finish on, one of the few, if not the only one where systems are documented from start to finish, and a little explanation about how things work in a structure that is exposed to 130degrees of temperature differentials throughout the year.

Here is a link that might be useful: Delores House

Rollie - thanks for the link to the house. Its very informative. I am sure it was work in itself to document it to that level. Its very helpful, but i now have a few questions .. :)

Do you have a link to where i get information on the Denarco seal, or is there a more commonly know name/product. I cannot find any website for this company and would love to know more about it.

On your Rim joists - you sprayed foam. Was this a contracted company - or a DIY Job. What product and thickness? I am very interested in at least doing this (DIY if possible).

If I were to use Rigid board in the bays, do I need an additional vapor barrier or the Kraft faced FG sufficient?

You also mention an Air barrier approach such as sealed polyethylene. Is this the External tyvek or another internal product - I am thinking internal from your wording?

Last question - with all of this air sealing, do i need some type of air exchange system?

thanks again

Rollie - thanks for the link to the house. Its very informative. I am sure it was work in itself to document it to that level. Its very helpful, but i now have a few questions .. :)
Do you have a link to where i get information on the Denarco seal, or is there a more commonly know name/product. I cannot find any website for this company and would love to know more about it.

Denarco is located at 301 Industrial Drive, in Constantine Michigan. You are looking for the 3/8 X 3/8 Urethene impregnated Sure Seal . It comes in 40 foot rolls. For the most part, it is an open cell gasket in its original manufacture, Open cells give it the flexibility to expand and contract when under load. When they impregnate the open cell gasket with the Urethene, then, what happens, is that when the gasket is fully expanded, its still somewhat able to breathe, but when it gets in the vicinity of 60% compression, the urethane bonds together to make an airtight seal. If the pressure is released, then, over time, the gasket will expand back to its original size. This makes for a forgiving seal, for when materials shrink and expand.

On your Rim joists - you sprayed foam. Was this a contracted company - or a DIY Job. What product and thickness? I am very interested in at least doing this (DIY if possible).

This was not my job, but I was responsible for finding the proper subs, and making sure that all of the systems were integrated together properly and documented during all phases of construction. To answer your question, yes, this was a contracted job. I dont know the name of the foam, per se, but it was a closed cell foam, in the vicinity of 3 inches thick at the rim joist area. If your rim joist is technical, then I would definitely look at a DIY spray foam, or getting a price form a foam contractor for the rim joist only. If the rim joist area is fairly straight forward, then I would simply rip 2" rigid XPS foam in, and seal it to the floor sheathing and the sill plate with either an expandable foam, or an acoustic sealant. One that is designed to stay flexible over the years. Like I mentioned in an earlier post, If I was using XPS sheets, I would get it in place before any subs showed up on the job that had to penetrate it, otherwise, it is just a lot more work.

If I were to use Rigid board in the bays, do I need an additional vapor barrier or the Kraft faced FG sufficient"

If you used rigid in the bays, and were not going to go with the ADA, then I would still install a interior vapor retarder. The need to detail it out to a T is for the most part, eliminated because of the vapor retarding characteristics of the foam itself. You could simply just staple up a standard 4 mil poly vapor retarder and be fine, knowing that you have a backup system in the foam. Personally, I donÂt like Kraft faced insulation, for too many reasons to explain here. I have seen some perfect kraft faced jobs, that were not good insulation jobs. Its just too hard to see exactly how the insulation is fitting the stud cavity, while it is easy to make it look good on the exterior, by simply doing a good job with the kraft facing. Yes, this is an installer error, and not really the kraft faced insulations fault. I guess is just a peeve of mine. Another thing, Kraft faced insulation for a 2X4 wall, is R11, while friction fit is R13.

You also mention an Air barrier approach such as sealed polyethylene. Is this the External tyvek or another internal product - I am thinking internal from your wording?
Like I said B4, do not confuse an interior air barrier with an exterior weather resistive barrier. In a heating climate, they serve 2 different purposes and are in 2 different locations. In a cooling climate, they can be one and the same.

Last question - with all of this air sealing, do i need some type of air exchange system?

Yes, you will need some way to manage your indoor air quality, whether that is a full blown air to air heat exchanger, or a simple exhaust only system, with allowances for fresh air intake. Either of these systems, will eliminate the need for "fart fans" in the bathroom, and are also quieter, because the fan is centrally located in the house or attic, and there are only intake ports into the bathroom. Current ASTM guidelines ask for 20cfm continuous, 24/7/365 from each bathroom, or equivalent. 10cfm out of a room that doesnÂt generate a lot of moisture, but still contaminates the indoor air quality, such as a laundry room, and 60 cfm in the kitchen, with a boost capability up to 140 cfm. DonÂt quote these numbers, but they are close.
This is for the house requirements only. It does not take into account ventilation for the range hood or any other appliance.

Take a read thru this site, it explains alot fo the reasons for building tight and ventilating.

rollie - THanks so much for taking the time to help. I appreciate it. I have some figuring out to do, but for the most part i think that i will price out foam for the rim joists and if it gets two $$$$ then I will just go with the rigid board option.

In My area, People are against any addl vapor barriers. Its always an area that confused me. With my cellulose quote, There was no addl vapor barrier recommended. With my FG quote -the kraft facing is recommended as the vapor barrier. I will talk with my builder this week on this

Anyway - thanks a lot again for the input - i will let you know how it goes

PS - excellent web site - very informative

doogan,

Even the true experts have problems with vapor retarders. The main thing to remember, is that one electrical outlet thats leaks into the stud cavity, will allow many times more moisture into the stud cavity than the whole rest of the wall. or possibly the house will thru diffusion.
Stabilized cellulose typically doesnt require a vb, mainly because of its denseness according to the cellulose people.

That line of thinnking is fine, as long as someone still addresses the bulk air leakage paths. H2O does not like to be in a gaseous state, it wants to be in a solid state, like water or ice, and is constantly searching for a condensing surface.

Ultimately, it your properly address the leakage rate of your house, you wont need a vapor retarder of any kind, irregarless of what insualtion you install in the wall, even fibreglass.

We went many years, without a vb in our ADA homes, until we lost a job to a competitor because he told the customer that we didnt use any vb in the wall. In our product, it wasnt needed, but, it wasnt worth losing a whole house over $30 of polyethylene, even if it was just added for cosmetic purposes and no, we still dont use it in a stabilized cellulose install, but we do still do everything according to the ADA approach with stabilized cellulose.

Rollie - Thanks. Glad to see its not just me confused about the VP

I do have another question for you, if you don't mind

Say i go with a sprayed rim joist, tight Drywall approach, Probabally either 1/2" Rigid in the bays held with foam or an inch of sprayed foam in the bays + R21 HD FG Bat. I will end up with a pretty tight house. I will seal all openings ( outlets etc)

How or what do i tell my hvac guy to size accordingly. Is there some number that can be plugged into the HVAC calculations that relates to a tight house? My HVAC guy is not really used of dealing with High Performance buildings so anything i can give him to get the system sized better i think would bring me closer to my end goal. I am using a Hybrid HP/furnace system

thanks

Doogan,

Im going to pass on that question, as its way out of my line, but yes, you should get different load calculations based on a high performance house.

I will page Energy Rater and have her give it a shot, Even though shes from the south, I would think she would be able to give you some guidance on the load calcs for a heating climate also.

I've been loosely following this thread, as I am also making insulation decisions. I'm a bit perplexed by a comment that keeps being made, and I was hoping that someone wouldn't mind cluing me in:

" You are in a heating climate at 5500 degree days, somewhat warmer than me at 7700 heating, and 670 cooling. "

What does this mean? Thanks in advance!

Very quickly

From Wikipedia, the free encyclopedia
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Heating degree day (HDD) and cooling degree day (CDD) are quantitative indices designed to reflect the demand for energy needed to heat or cool a home or business. These indices are derived from daily temperature observations, and the heating (or cooling) requirements for a given structure at a specific location are considered to be directly proportional to the number of heating degree days at that location.

More specifically, the number of heating degrees in a day is defined as the difference between a reference value of 65°F (18°C) and the average outside temperature for that day. The value of 65°F is taken as a reference point because experience shows that if the outside temperature is this value then no heating or cooling is normally required. Occupants and equipment within a building usually add enough heat to bring the temperature up to a more comfortable level.

Suppose, for example, that the average temperature for a given day is 55°F. Since this value is ten degrees lower than the reference point of 65°F then one would say this is a ten degree-day. Obviously, the outside temperature is not always constant, so one needs a method to determine the average temperature. A simple way to do this is to compute the arithmetic mean of the high and low temperatures for the day. While not always correct, this is sufficiently accurate for most purposes and is done for practicality because these temperatures are always recorded by the weather bureau. Thus, in the previous example, if the high temperature were, say, 65°F and the low 45°F, then the average would still be 55°F for a ten degree-day.

65°F is known as the "base temperature" of the degree days. Degree days are commonly found with a base temperature of 65°F or 18ºC, and 15.5ºC is common in many countries such as the UK. However, heating and cooling degree days can actually be calculated using any base temperature - the most appropriate base temperature to use depends on the application (e.g. the temperature that the building is heated to and the amount of heat supplied by people and equipment).

Heating and cooling degree days can be added over periods of time to provide a rough estimate of seasonal heating and cooling requirements. In the course of a year, for example, the number of heating degree-days for New York City is around 5,000 whereas that for Barrow, Alaska is over 20,000. Thus, one can say that, for a given home of similar structure and insulation, four times the energy would be required to heat that home in Barrow than in New York.

What you are looking for is a load caluclation.
Manual J is provided by hvac company (good..IF they have experience and use correct inputs..bad if they don't understand where to contribute the air sealing benefits..and worse if they only use rule of thumb (sq ft per ton) sizing)

an independent company to run load calc

or by the hvac mfg..the only issue I have with this..is that the mfg will back the hvac company and you have to have a real sense of doing the right thing when you are providing the product being sold. Otherwise you have a 5 ton system..only cause they don't make 6 ton systems in residential..when a 3 ton would have provided you with what your house requires.

IMO..here in the land of great oversizing..an independent company to provide load calcs is the best thing.

When providing the plans be sure to include insulation details, degree of air tightness of house and duct system, types of windows, orinetation, and location of hvac within the house.
Man J sizes the hvac system, Man S is for duct sizing and Man D is for design of duct layout. All three are worth the investment..be prepared to pay for this.

Then using the load calculation you can then shop for a company that will do the install as per calculations.

As always, duct leakage should be minimal (5%) and all ducts should be mastic sealed.

When you build a 'tight' house (energy efficient)you plan for a tight house, but untill the house is done, it isn't always necessary to add make up or fresh air. Less than .25
air changes per hour require additional air. But until the house is tested with a blower door (and ducts tested to make sure leaks are sealed) to determine how many air changes you have achieved, you just don't know.
I've seen a lot of homeowner's buy ERV's (HRV for your area) only to never achieve enough of a negative pressure on the house to make ERV necessary.

Still in all, the details of the air sealing, and duct sealing may be yours to do if you want it done properly.

Best of luck..

Use Blown in Blanket Batts. Nice tight insulation - very affordable about $.92 per foot and R23 for 2x6 walls.

I hadn't seen this one. The Canadian Construction Materials Centre approval testing (11790R) shows R values of 14.3 in 2x4, R 22.7 in 2x6 walls, vs. blown cellulose values of R12 and R19, and blown mineral wool factors of R 12.8 and R 20. (I converted the metric wall measurements.)

This (video) blown-in batt installer claims that blown-in fg costs 50%-60% more than conventional batts but pays back in energy savings in New England in two years.

It's what we have in our wall cavaties as mentioned previously. Cant speak for payback or the mfgr's claims, but we are impressed with the density as well as it getting behind electrical, plumbing, and corners where normally there are voids with standard batts. The rockers were whinig about the staples as they are placed about every 1/2" on ours, but they survived. I had to pull some out of a stud space to run another electrical feed, and it was amazing how much product came out of a 14-1/2" x 2x6 stud space!

It's what we have in our wall cavaties as mentioned previously. Cant speak for payback or the mfgr's claims, but we are impressed with the density as well as it getting behind electrical, plumbing, and corners where normally there are voids with standard batts. The rockers were whinig about the staples as they are placed about every 1/2" on ours, but they survived. I had to pull some out of a stud space to run another electrical feed, and it was amazing how much product came out of a 14-1/2" x 2x6 stud space!

sorry for the double post...pete & repeat walked across the bridge. Pete fell off, who was left?

I was taken by the marketing phrase "blown-in blanket batts". It seemed a contradiction.

But it offers an another alternative for those buyers interested in energy saving. As a spec builder, I wouldn't bother. XPS sheathing costs the same as OSB or gypsum while offering vast benefits in terms of air tightness and insulation value.

There's a lot of leakage from the edges of the drywall as well (in addition to the penetrations). The face of the wall leaks very little.