So cape cod house as in a 1-1/2 story. So you are limited in space as far as insulation goes for a good amount of the ceiling/roof. Limited to the depth of the rafter beams. Here is a general idea what you are looking for in ventilating the roof deck, an air space above the insulation. That requires either spacers below the roof deck for air flow or baffles installed which take up space for insulation. Ventilation would be required for any insulation other than spray foam.

There is a reason everyone is recommending closed cell spray foam, you achieve about R6 per inch with it and you wont have to ventilate. Roxul is about R4 per inch and you have to ventilate the roof deck. If you require insulation inspection on your permits you may fail inspection with the roxul.

Perhaps there is a happy medium, use the closed cell foam where needed and roxul where you can use it and achieve correct R value. However, you would still have to ventilate the roof deck wherever the roxul was used, so more penetrations in the roof. You would be better off doing the spray foam and no ventilation, this is called a closed attic system aka unvented conditioned attic.

Well, no, two stories, but the second floor has the slanted roof in the front and a full dormer in the back. I suspect the dormer was added at a later time. This was built in the 1950s, and it had the original Rockwool insulation when we moved in which is what is being replaced. Some previous owner had added some fiberglass batts above the rock wool, on the deck of the space above the 2nd floor.

No, insulation does not require a permit and I've been advised, that what ever current code is, it is for new construction and not retrofit.

There is no possible way, under any circumstances that I would use foam spray. If it comes down to a potential health threat, or energy efficiency, a healthy home is going to win every time. Besides, more and more people are moving away from spray foam. Lots of stories of sick buildings and homeowners moving out of their home and once it's in, how do you remove it, if it is a problem? And recently it's been reported that the navy has been having fires on ships due to foam insulation. So, I think I am on the right track in attempting Rockwool insulation and not foam.

Perhaps the proposal I was given did take into account some kind of roof deck ventilation that I've forgotten, I'll have to ask. Are you saying that you cannot have a closed system with any other insulation?

Do I understand it correctly, that the R value guidelines or code, is to save energy? And if we continued along with what we have had all this time, well, that was what used to be acceptable. Now the only reason they moved to a greater R Value was due to the use of foams. Which from my perspective was short sighted and a mistake. It's too bad that they didn't instead change the structure of homes that allowed for deeper rafter bays to allow for larger amounts of Rockwool, which is non toxic and naturally fire resistant.

Here is an article that might be of interest…..
Mineral Wool Boardstock Gaining Ground in Homebuilding.

They increased R value recommendations to save energy yes. They did not increase R value recommendations due to the use of foams. Foam achieves a higher R value inherently, it is a sealant so it seals air leakage, and it is either a vapor retarder (open cell) or a vapor barrier (closed cell).

I agree with you that rockwool is a good product, you just have a limited amount of space for the insulation and a baffle for ventilation.

If you want a safe spray foam you should look at the foam-it-green company. Their spray foam is sold as having no CFCs, Penta-BDEs, VOCs or Urea Formaldehyde. https://www.sprayfoamkit.com/

Not sure you got my point - they only reason they could increase the R value recommendations was due to the use of foams.

I certainly don't want to debate the use of foam, as I'd already made up my mind I don't want to use it. I have multiple reasons for finding it to be unacceptable. It is a plastic. It's not a natural material. And the link you provided appears to be an advertisement from the company that makes it or sells it.

But I thank you for your thoughts and information. We may disagree, but that's okay.

Your original question was long and suggested solutions before adequately defining the problem so I wasn't able to figure out what you want to insulate. Is the space under the roof occupied? Is there an attic and, if so, how is it currently ventilated? Are you insulting the attic floor or the roof rafters or some of both? Are there any cathedral ceilings? Are there under eave spaces? Are the rafters only 2x6's? Can they be increased in depth? How much of the project will have finishes removed?

If you want useful advice draw a plan and a section through the house and label the sizes of the structural elements and indicate what space is occupied. Don't worry about vapor retarders until you have designed the building envelope.

I'm not sure what you are asking.

are you having problems defining the thermal

boundaries for the install of rockwool?

are you objecting to the depth of insulation actually

required?

what is required for your climate?

while we don't have issues with ice dams here in La.,

here are my thoughts fwiw...

its all about air movement. stopping heat gain/loss

through ceilings into attic is a huge issue.

but...

if you have an air tight ceiling (air barrier) with insulation

on top ( thermal barrier) then the ice dam probability would

be reduced. but add in a recessed light and you have air

movement through the insulation & a de-rated/performing R-value

then you would have more of a chance for an ice dam.

the moisture issues I've encountered have more to do with

the example above of a compromised area of thermal

and air barriers.

prior to insulating...all air sealing should be done.

sealing the penetrations from living space into attic space.

if air isn't moving through the insulation, then it can perform

as spec'd.

this holds true for all insulation, foam just does the air seal & insulation

in one step. otherwise one has to manually seal these penetrations.

this is the step many homeowners miss out on.

oversizeds cut in ceiling for bath fans, recessed lights, speakers

stove vents, hvac supply & returns, fireplaces...plumbing & elec penetrations

these openings should be sealed to stop air movement

through the insulation & into the conditioned space below.

a blower door test would pinpoint the leakage areas to be sealed.

any and all attic work completed prior to insulation.

"Now the only reason they moved to a greater R Value was due to the use of foams"

code standards are for the minimum allowable by law.

(note MINIMUM..the least amount acceptable)

the use of foam products has not changed these standards

as all insulation products are rated by R-values.

building a tighter home is achievable by the use of foam insulation

but by far not the only method of achieving this goal.

kind of an interesting thread.

most of my conversations go like this...

"ok, this meets code, what is the best we can do...??"

best of luck.

JDS and Energy_Rater - - Sorry for the length of my post and that it was not clear. I do find it confusing and I guess that comes across.

I’ll try to draw something up, although my drawing skills are pretty basic. [g]

This drawing is to scale of the current layout on the 2nd floor with my notes.

This 2nd drawing I just quickly drew up to give you an idea looking at the house

from the South end of the building. It is not to scale.

We have a 2nd floor of a Cape, front of the house has the typical Cape roof with no windows or dormers on the front. The back has a full dormer being used by two bedrooms. The stairway and hall are in the middle of the 2nd floor and on the other side of the wall of the hall, on the front is storage space from one end of the house to the other, on the front of the house. See the drawing.

So we have to insulate above the second floor, which is only accessed by a panel in the ceiling of a closet, and we have to insulate the storage space from one end of the house to the other.

We are planning to work on the ceilings and walls on the second floor, so we can have better access to the area on the dormer to try to insulate that as well as we can too.

We’ve been told that we do not currently have ventilation, except for the usual gable end vents. We have soffits with vents, but they appear inadequate and out of date and do not know if they are blocked in any way. We have had no evidence of mold. It is definitely not air tight. We had rock wool on the under side of the sloped roof on the front, between the rafters, not on the Knee Wall or the floor of the storage space. So the storage space is not freezing or super hot. Above the second floor there was rock wool between the floor joists? of the attic space, or do you call that the deck? There are 2x8s in that area. I believe. And fiberglass bats were added on top of the rock wool.

The roof rafters are all 2x6s. The floor joists on the floor of the space above the 2nd floor are 2x8s.

I’m just trying to insulate the storage space and the space above the 2nd floor using only Rock Wool insulation or Rock Wool boards without causing a problem with mold and preventing ice dams.

Amy - I just saw your post. Sorry, I don't take surveys or click on links from strangers. I did look at your profile and see you have posted to a few threads asking the same question. That's not what we do here.

Recommended levels of insulation

https://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_insulation_table

With rockwool at R4 per inch, you would have to increase depth of the joists on the roof in the storage space to get you to R 49 approx. to 12" depth insulation + 1" for baffle vent. Those are 2x6 so really only about 5" depth so you need 7" more depth so expect to add an additional 2x8 depth to each joist. And those joists will need to be sealed very well to stop air from leaving the house while venting the roof deck with a 6 mil vapor barrier taping every seam.

It is either that or insulate the floor and wall of the storage space and consider that space as a cold zone or part of the attic.

The upper attic you can insulate normally, it will be tight on the back edge but you should achieve R 49 with the ceiling joists and roof rafter spaces on that back edge.

I don't see how I can increase the depth by 7 inches. What would we be talking about ripping out the roof all together and starting over with 2x12s? And if it requires extensive structural changes to bring the R value up to R49, then doesn't it make sense to accept whatever level of R value that you can achieve with the space you have?

Having 4 to 5" of roof insulation using the 2x6 space is not acceptable. Your heating/cooling bills will reflect this. Also, 2x6s might not be able to handle the weight of both the roof and increased insulation by itself if you were to attach two layers of comfortboard to the rafters. I will let some of the builders give ideas on how to restructure the joists, I have ideas but am not sure they are correct. Does not necessarily mean a new roof, just beefed up structure underneath.

Okay, but we were talking about around a $3,000. bill from Mass Save to come in and add cellulose, with no foam. Then we were getting bids from some who said their average charge for insulating our size house, using a combo of materials would be $6,000 - $7,000. Now switching over to all Rockwool, it's creeping up there over the $10,000. mark. And if you are talking about restructuring all the 2x6s in the roof of the house, I think you could be talking about 4x that much money or more.

So, that to me seems more unacceptable, then that our heating and cooling bills will not be lower. As we are now, with the insulation we now have, our fuel bills are not outrageous. We have cellulose blown into the walls, 20+ years ago and our house is not uncomfortable.

The obvious answer is closed cell spray foam. You should do some more research or live with the insulation you already have.

Its your house and your heating bill. You know what your dealing with more than us. As far as blown in insulation, the insulation above you is more important than in the walls. We all know heat naturally rises and it needs to be stopped or it will keep going up. Heating dollars leaving the roof. Now you want to have 5 inches of insulation above you, then do what you want but I dont believe any contractor will believe it is a good idea. You have limited space on the roof deck for insulation and will only use a certain product so do what you will. I DO agree with you that rockwool is a good product, you just wont have enough on that roof deck.

Remember the other option is to treat your storage space as an attic and insulate the floor and hallway wall, weatherstrip/seal the door, ventilate the space, and consider that attic storage. Technically it is attic space where you currently store stuff, and that is fine it just would need to be treated as such.

Fire Hazard of Polyurethane and other Organic Foam Insulation

Massachusetts Fires Tied to Spray Foam Incite Debate

EPA Raises Health Concerns with Spray Foam Insulation

What happens to the environment when homes with these products burn.

Foam Insulaion Doesn't Get A Free Pass from Safety Law in CA

Spray foam insulation can make some homes unlivable

JDS - I've done research, but I guess I am doing research that you are not doing. And the above links were collected in about 15 minutes on Google. And that is weeding through all the PR pieces put out by the industry trying to convince people foam insulations are the best thing since sliced bread.

I have a lot of confidence in my position.

Vith - I don't disagree at all, that the insulation above is the most important aspect of energy efficiency. You don't have to convince me of that, I do understand it.

I called the Rockwool manufacturer and explained my dilemma and I was told that many homeowners install Rockwool by laying it between the floor joists of the attic and then adding a second layer perpendicular to the first on top of that. That would certainly give me a higher R value. And it would seem that it is already being done by others using the product.

I'm trying to evaluate whether insulating the knee wall and the floor of the storage space would offer me better insulating opportunities. Not sure if that would allow for the space to be used for storage. And how do I get thicker amounts of rock wool in the wall and floors of the storage space than I can do on the underside of the roof? I'm not really following that suggestion, sorry. We are talking about defining the envelope of the building, right? And in this suggestion then, we would be taking a large portion of the building and leaving it outside of the envelope, is that right?

prairiemoon2 z6 MA, You are not reading the information carefully enough to understand it.

In the first reference, OSHA is primarily concerned with workplace safety and the article is about the possibility of "exposure to large scale fire conditions" and construction conditions like "storage of exposed foam, incomplete installation, ... improper application and disposal practices, poor housekeeping conditions, and ... exposure to open flame from allied trades" as well as on large ships. That's not what you need to be concerned about. In your case, the use of a thermal barrier (drywall or intumescent coating) is entirely adequate to protect your family from danger in a fire long enough to escape. Proper early warning alarm systems and escape routes should allow you to be elsewhere long before fire reaches the insulation in your roof.

- Your second reference is about "three house fires that were ignited while insulation contractors were installing spray polyurethane foam". Any competent installer knows to apply spray foam in layers to avoid heat build up especially in a confined space. If that is your concern, conduct an on-site meeting before the insulation is installed to make sure the proper procedures will be followed.

- The third reference is concerned with exposure to installers especially DIY home-owners. It makes no conclusion about post installation exposure: "I think you have to be careful when you discuss the toxicity of spray foam," says David Price, environmental scientist in the indoor environment division of EPA's Office of Air and Radiation. "I have not seen any information at this point that there is any hazard to occupants." While Price supports EPA's decision to gather data on possible post-occupancy issues with SPF, he doesn't want the public to "find the accused guilty before you hear the case." If you want to wait for more information do so but don't draw conclusions based on no information.

- The fourth reference is about pollutants released in a house fire. Materials that contribute to toxic gasses are not only polyurethane foam but PVC, nylon, and other polymers. The conclusion of the article is provided by Fire Lt. LePage, “My advice to people is to stay away from the fire, to stay away from the smoke." Of far greater concern is clear burning of farm lands, leaf burning, wood burning fireplaces and forest fires.

- The fifth reference is concerned with reducing health risks to installers in California.

- The sixth reference is concerned with improper installation. These situations occur for one of several reasons: the installer sprayed the foam too thickly in one pass; the chemicals were not heated to the correct temperature; or the substrate was below 55 degrees F. Here again the best protection is a pre-installation meeting and perhaps on-site supervision by your agent.

I would say you have yet to do any substantive research because you are not aware of the real issues and so much of internet information is from competing insulation trade groups. If you are not comfortable with using foam insulation for any reason you should avoid it but you should not blame the material as if your opinion was based on real research.

In your house, to improve the R value of any exterior element using rock wool it will probably be necessary to alter the structure or add furring. The break even point may not occur during your ownership so it might be wise to make improvements in your heating system and controls first.

In Massachusetts a building inspector will sometimes allow an attic to be sealed (unventilated) with dense pack cellulose instead of spray foam.

And how do I get thicker amounts of rock wool in the wall and floors of the storage space than I can do on the underside of the roof?

The wall can follow wall insulation rules instead of roof insulation. Doesnt need to be as thick, also, a layer of comfort board could be able to be applied to and supported by the wall if needed.

Your floor joists should be thicker than 2x6. Also not supporting the roof, and also as you noted you can install batts perpendicular across the floor above the joists. You would loose the storage space but attics cant always be used as storage (mine isnt).

Whoever decided to use 2x6 for your roof did not do you any favors. The weight of the sheathing and a couple layers of shingles is about all it could handle.

Here is some more useful info and diagrams.

http://www.energysmartohio.com/blog/how-to-insulate-and-ventilate-knee-wall-attics

JDS - Well, I gave it a shot to try to get some help here, but I guess I’m going to have to find help somewhere else. I’ve stated from the beginning and all the way along, that I was not going to use foam spray products and that I didn’t want to get into a debate about it. What is the point?

You seem to have a long standing opinion about the value of foam products and you accept their shortcomings and feel the precautions and work arounds to make the product useable are good enough. I don’t. You’re not concerned with the chemicals released into the atmosphere when they are burned, or with long term disposal of these products and I am.

You point to the EPA saying they are not aware of enough information available to consider them unhealthy. I guess you can ignore the fact that a class action suit has been settled in Canada against RetroFoam of Canada. And there are other class actions suits being filed against some of these manufacturers of foam products, not just in this country but in others. So, I guess there are homeowners who would disagree with you that these products cannot be health hazards.

On the other hand, I have not seen any class action suits against the manufacturers of Rockwool.

Apparently, you don’t have any recommendations to offer in order to maximize the R value of the Rockwool as an insulation material for our project. That’s fine. The suggestion has been made, to alter the structure to allow for it’s use. That is not an option that makes sense for us.

Thank you for your time.

Energy Rater - Thanks for the answer to my question on the two layers of batts and for the link for the how to on air sealing. I appreciate it. :-)

Vith - Thanks for that explanation about the difference between insulating the wall and the underside of the roof.

Yes the floor joists are 2x8 in the space above the 2nd floor. That space was never capable of being used for storage, there is nothing in that space. It was the space under the eaves on the second floor that we use for storage.

Thanks for the link - diagrams are always a help. :-)

I have no recommendation other than foam because the framing is not deep enough for any other option. I think I made that clear. You are the one who decided to debate the use of foam insulation. You ask for advice and then lecture us on things you know little about.

OP, do you see the kneewall sealing info on page 5?

this would be the best way to seal & insulate the

kneewall/attic.

good detail in the southface pdf.

as for keeping your storage area, insulate the joist bay, then

toenail 2x's perpendicular to the existing joists.

insulate. use screws instead of nails, and deck the

storage area with screwed down decking.

its a process, but not that unusual in my experience

in attics.

best of luck.

Energy - Rater - Yes, I see the sealing information on page 5. Very detailed graphics, which really help. And I can use a non toxic caulk rather than the foam spray.

I’m sorry, I am knowledgeable in the garden, but for some reason, the problems with the insulation are a struggle for me. Your description of keeping the storage area….

What area is the ‘joist bay’? The floor of the space? What do you call the 2x6s that support the roof above? Are you suggesting that I fill between the joists on the floor with insulation and than add like a plywood deck on top of it to allow for storage?

This storage area will now be outside the envelope of the building correct? I guess I’m just wondering how cold or hot it will become and the affect on the materials I would store there.

I understand that using the knee wall for the outer edge of the envelope allows for deeper insulation without much additional construction, but I wonder if I should still be adding rock wool batts to the underside of the roof, between the 2x6s and if I do that, maybe that would keep the storage area with fairly even temperatures.

Thanks...

One other idea….what would be the effect if I put rock wool in the bays on the underside of the roof in the storage area and put wallboard over it in addition to insulating the floor and knee wall?

JDS - I’ve expressed my strong opinion that spray foam is not for me and I’ve given reasons why, only after having said I didn’t want to use it, and the next comment suggested I try to use it any way. Then it was dropped. It was you, JDS, who brought it back into the conversation, by insisting that “closed cell spray foam was the obvious answer and I should do more research.”

If you have interpreted my comments as a lecture, I think you are reading into it something that was not there. My responses certainly felt like a defense against you disputing my own position on foam.

rafter bay is between rafters. rafters are framing for roof.

joist bay is between ceiling joists. ceiling of living space. from

in attic the joist bay is the attic floor.

"Are you suggesting that I fill between the joists on the floor with
insulation and than add like a plywood deck on top of it to allow for
storage?
This storage area will now be outside the envelope of the building
correct? I guess I’m just wondering how cold or hot it will become and
the affect on the..."

yes fill joist bays with insulation. install perpendicular joists toenailed

into existing joists. fill those bays with insulation, deck & store on top.

yes will be in unconditioned attic, outside of the thermal boundary of the bldg.

temps in attics can be extreme. maybe you need to clean out closets for

items you can't store in attic?

were you somehow hoping to achieve a conditioned unvented attic?
your posts aren't clear.

are you suggesting insulation in rafter bays & wallboard (sheetrock??) over it?

is this to create a 'conditoined' space for storage items?

when the roof leaks & soaks through the

insulation & drains down & shows up at the walls...

you have a huge mess to contend with. not something I'd

ever recommend.

much easier to create storage in house or even

storage shed.

best of luck.

Thank you Energy Rater - I'm going to have to digest all that.

The simple answer is that if you want to have an R rating which is high with a material with a low R/inch, then you have to have more inches. This would probably involving replacing and re-framing the roof. Sometimes taking a principled stand costs more and you have to decide if it's worth it. (Of course, "costs more" could mean just using less insulation and paying more for your energy). There are many procedures in the building trades developed to reduce costs and/or improve performance which I don't like, but have learned to live with. For example, drywall rather than wet plaster, plastic pipes instead of copper, non-metallic sheathed cable (Romex) rather than BX or conduit.

A very sensible comment mtvhike - you are right of course. According to your big picture view, I have three choices, replace and reframe the roof, which I would only do, if I were going to add a third floor addition, or use the foam, save the money and live with it, or use a reduced amount of insulation and pay higher energy prices. Every person might make a different choice.

I am still considering using some rigid foam board in a 3-4ft section along the lower part of the dormer roof where it's impossible to get much else in that small space and using rock wool everywhere else.

I'd also have the option of lowering the ceiling, but I don't believe I'd have enough headroom.

I also prefer wet plaster to drywall. All our first floor walls are that and it is a quite noticeable difference in quality and longevity. A previous owner used drywall on the second floor. We have some added plastic pipe in a couple of places and I hate it. I'm not familiar with the difference between Romex and BX.

In some cases it may be that the difference in using one product over the other, is for reasons of quality, but in others, it becomes known after something has begun to be commonly used, that the newer cheaper material has health consequences. In those instances, it's more than just 'taking a principled stand' to me. Some people feel the health risk is a reasonable one and doubt there is enough exposure to be concerned. To me, when it gets to the level that homeowners are bringing a class action suit for health problems caused by using the product, that's enough evidence for me to feel the risk is not reasonable.

You do see my dilemma and I appreciate your comment.

If your concern with foam products is the possible outgassing of hazardous substances, then you should consider a HRVS, or Heat Recovery Ventilating System. In this system, fresh air is brought into the house and passes through a heat exchange system. Inside air is exhausted through this same heat exchange device, transferring its heat to the incoming outside air. The two air flows are separate, and only the heat is transferred. Of course, the maximum heat transfer would be 50%; i.e. if 65 degree air is being exhausted and 5 degree air is being brought in, then in a perfect system, the two air streams, after passing through the heat exchanger would be the average, or 35 degrees. But nothing is perfect. Even so, such a system is highly recommended (and maybe even required in some jurisdictions) for any superinsulated home which is very tight. Even if you don't have the foam insulation problem, many household products such as cleaning fluids and furniture may release toxic gasses, so an HRVS can only help. The only downside is that they aren't completely quiet. In my new, superinsulated house, the only thing I can hear when I am sitting in the living room at night, is the HRVS and the refrigerator in the kitchen.

Non-metallic sheathed cable is the most commonly used wire in residential settings (although I'm pretty sure electric codes don't allow it in such cities as Chicago and New York; Romex is a trade name for one brand of this and, like Kleenex and Scotch Tape, is commonly used for any brand. BX is a flexible, metallic sheathed cable which was used prior to Romex, and still is required for some applications.