I needed more rock wool insulation – a whole lot more. It’s for the second floor exterior walls and the attic.
My primary rock wool supplier, the Chicago Green Depot, went out of business about a year ago. I needed to find a new supplier!
Back in the day, the Chicago Green Depot had the best priced rock wool. I got the last batch in early 2012 for around $35.00 per bundle (60 square feet of 3 1/2 inch rock wool batts). All other sources I contacted, including your typical big box home improvements stores, always came in more expensive.
This time around, April 2013, didn’t seem to be any different. The Home Depot had the bundle of rock wool listed for around $43.00! I thought, though, that it couldn’t hurt to double check the pricing for 120 bundles at the Pro-Desk in my local store.
The printout I was handed listed a total of $3,340.80. That breaks down into a unit price of $27.84 per bundle plus tax. That is a considerable price drop from the listed $43.00 … around 35%! This is even less that the first batch I bought for the basement installation.
Do I need to say that I was a very happy camper?
Why that 35% price drop? If I go to the Home Depot and place an order over $2,500, I am referred to – what they call – the bid room. Because I am buying in bulk, I have access to a different pricing structure. That said, I would be surprised if that 35% discount will last for long; this may be part of a current promotion.
The significance is that this is the first time that I bought a substantial amount of building materials from a typical big box home improvement store. Materials for a deep energy retrofit like ours were in the past not available, hard to get special orders, and/or too expensive.
Is this a sign that green building materials are on their way into the mainstream?
I identified the existing double hung windows on the 1st floor as a weak point in our insulated building envelope. There is another energy leak that should get fixed, now that the radiators are up and running. And that is the kitchen back door leading to the back porch.
Don’t get me wrong. This is a very nice solid core door. Well, it became very nice after our friend Anne had removed all the paint. The door was so nice, that we decided to repurpose it into the front door to the 1st floor unit.
What the door didn’t have was a high enough insulation value. Because the kitchen back door is an exterior door, separating the conditioned from the unconditioned space, it must have an R-value of at least 5.
That really narrows down the options. I ended up with an energy star door, steel skin with insulated foam core. It was a custom order to fit the existing opening.
Fitting the door was a little tricky because the door buck was not perfectly square. I also had to remove and replace the old threshold.
Last but not least, a well insulated door is not worth much if it isn’t air tight. I had plenty of weather stripping left which I mounted on the door stop. That should take care of any draft and losing precious heat to the cold outside.
A deep energy retrofit like ours often conflicts with standard construction practices.
Put an electrician in a situation like the one pictured above, and it is very likely that you find the electrical conduits installed behind the wood framing – because that would be the easiest and productive way to install it.
That actually happened to me in the basement unit, while I was not looking. Before I knew it, all the data cable wires were placed in, what I call, the insulation zone.
The primary reason why we don’t want any utilities in the insulation zone is to prevent thermal breaches – or weak links in the insulated envelope. Think of it this way:
There is a temperature gradient in the insulation. In wintertime it would be from cold toward the outside to room temperature on the inside.
The farther I place the electrical conduits towards the outside of the insulation cross section, the cooler they will be. And because the conduits are tubing that connect to the inside of the rooms at outlets and switches, they also become a perfect conduit channeling that cold into the cozy room interior. This would create a perfect thermal breach.
The farther I place the electrical conduits toward the inside, the more I keep the insulation cross section intact and the less likely of channeling cold temperatures into the rooms.
There is a new line of thought emerging that takes the issue of avoiding thermal breaches to a new level. That is, keeping electrical and plumbing completely out of airtight walls with a service cavity or service core.
The principal idea is to add a small wall to the existing wall on the interior of the building. All it takes is to fasten two-by-two furring strips horizontally to the insulation wall. The one-and-a-half inch cavity or core would be deep enough to accommodate electrical and plumbing while disentangling it from the insulation.
I do like this idea, not only because it eliminates thermal breaches, but because we are about to face the tedious task of fitting the electrical into the insulation wall. And while doing so, we have to keep it as close to the room interior as possible.
So why don’t I just install a service cavity or core? Because we have already reduced the room size by six and a half inches to get an R-value of 27. We don’t want to reduce the room size any more. And even if we did, I still would opt to add insulation into the service cavity to drive up the R-value.
Where and when could a service cavity become handy? In retrofit situations where the building is insulated from the outside, or, where the R-value of the outside wall is already at or near R-40.
You can read more about service cavities or cores and their applications at the GreenBuildingAdvisor.com blog “Musing of an Energy Nerd.”
This is a very good day – for all those who own a masonry building, who are interested in a deep energy retrofit and who would like to insulate the masonry walls from the inside.
The frustration has been that there was next to no information available on the pros and cons of insulating the interior of masonry walls, or on how to go about it without damaging the structure.
Regular readers of the blog will remember my epic search for reliable and sound information on this subject. At the time, I came across one document – to repeat, one document – on this subject, also published by Building Science Corporation.
Do you really want to make an insulation decision of this magnitude based on one document? No, not really. But that’s all that was out there, in addition to some other documents that offered tangential information and the occasional anecdotal evidence.
We had to knit the little information we had together and hope that we got it right. I am glad to report that I see our decisions confirmed, after having read the executive summary of the new research report.
If you have done research yourself on the subject of deep energy retrofits and how to insulate, you will have noticed the abundance of information available for framed buildings or new construction. I cannot fathom why the existing masonry building stock, which is rather significant in metropolises like Chicago, is left without resources.
If we are to get serious about reducing our energy consumption and carbon footprint, we have to get serious about retrofitting the abundant existing masonry building stock. Building new and green can’t be the solution alone. We have to begin to reuse the resources we have.
Rather than documenting our thought processes, decisions and installation efforts, this time I need to solicit ideas from you to inform our next task at hand:
I would like to get the limestone foundation wall insulated from the outside. The foundation wall is all below grade except the top four inches, which stick out above grade. There are a number of different steps involved:
Excavate around the foundation wall down to the footing
Re-point the exposed foundation wall
Install a foundation drain around the entire footing
Install flashing at top of the insulation assembly
Back fill and clean up
It is step #6 in this process I need help with. I can’t figure out how best to go about the flashing.
Here are two sketches: 1) The foundation wall as is, and 2) the foundation wall with the insulation assembly. (Click on the images for a larger view)
The red line in the second image represents the flashing component I need. It prevents any water from entering into the insulation assembly and thus keeps the foundation wall dry. The flashing will need a water tight connection to the brick wall and needs to extend over the water proofing component.
What would be a suitable material or product to use? Ideally I am looking for a prefabricated product that I can buy off the shelf. If not, I am open to fabricating something.
Well, not quite that solid. Actually, mostly spongy, but still rock and still déjá vu.
I am talking about 35 bundles of rock wool (also known as mineral wool) that I picked up at the Chicago Green Depot. The bundles don’t look very happy sitting in the corner and are sort of asking for our attention.
The three and a half inch thick rock wool batts are the final component in our insulation assembly. They add an additional R-15 to the R-6.5 of the one inch closed cell foam and the R-7 of the two inches of open cell foam. That brings the total R-value of the insulation components up to 28.5.
Why did we finish the insulation assembly with rock wool and not just continue with spray foam?
Rock wool is significantly more economical compared to spray foam. The batch I bought for the 1st floor cost $0.17 per board foot. Open cell foam runs around $0.40 and closed cell foam around $1.00 per board foot.
The rock wool batts are an ideal medium to install between framing. The contiguous gap between the framing and the brick wall on the other hand is easier to fill with a medium like polyurethane spray foam (SPF).
There are a number of other good reasons which led to the decision to use rock wool. If you like, you can read up on them in a previous post.
We had a good test run installing the rock wool in the garden unit about a year ago. Cathy actually has become sort of a master in fitting the batts between the joists, studs and around obstacles like PEX tubing. I set her on the job and before I knew it, she had finished the ceiling.
The walls were a little more involved as I first had to cut back the excess spray foam, so that the batts would actually fit. Our friend Anne was kind enough to help with the installation and we blew through half the building in one day.
With the 1st floor insulation finished, it should now become a little cozier, even though we don’t have the radiators up and running yet.
But I am glad to say they won’t stare at me much longer. Bit by bit we knocked one item after another off the task list r and we are finally ready to fill that gap with the open cell foam. It is time to call the insulation crew back in!
Spray polyurethane foam (SPF) doesn’t come cheap. To make this investment worthwhile, it is important that the SPF is applied properly, whether it is the closed or open cell kind. Getting the SPF installation right is more difficult than one may think. Here are a few observations that could help with quality control.
Lurking behind the studs
The saying is that open cell foam will fill all the nooks and crevices due to its extraordinary expansion rate (listed as up to 100 times it original volume for open cell foam). That is true, as long as the nooks and crevices are small enough.
The two inch gap right behind the studs is too big to get filled by the expanding foam, as you can see in the schematic section of the wall below.
To fill that gap, the spray foam must be applied to the surface directly behind the stud. If not one may end up with thermal breaks like the one shown below.
You can actually see in the video of the closed cell foam installation how the applicator carefully sprays a band of foam right behind the studs before filling in the open wall space.
Cornered
Building corners are known as the most vulnerable areas in the thermal envelope. To add to the thermal integrity, we minimized the framing, which in turn allows for more insulation in the corner.
That, however, leaves us with a significant gap behind the framing. Unless properly filled with insulation, this can turn into a significant thermal break – a cold building corner – that could cause condensation followed by moisture and mold problems.
If open cell spray foam is applied along the framing with the assumption that it will expand into and fill the corner space, think again.
I learned this the hard way, by drilling a few holes into the corner framing so that I could peek into the gap behind.
Wall junctions
Equally difficult are the areas where a perpendicular inside wall abuts against the outside wall. We structured the framing for the best insulation yield, which again creates a space behind the framing that is equally large to those at the building corners. The thermal break problem repeats itself, as can be seen in the schematic cross section below.
Whether a building corner or a wall junction, to fill the gaps, the open cell spray foam must be applied to the area directly behind the framing.
Even if done this way, it needs to be applied at a much higher rate to fully fill the depth of the gap. If not, the space ends up only partially filled and insulated, which is not acceptable, considering the investment at hand.
You’ll know when the space is properly filled, because the open cell foam will begin to squirt out from all the nooks and crevices in the corner or wall junction framing.
Floor joists
We applied a layer of open cell foam to the garden apartment and 1st floor ceiling to create an air seal between each unit. That air seal is not a given, as in some instances the open cell foam may begin to separate from the floor/ceiling joists, leaving behind a small gap.
This can be easily prevented by first spraying out the corners of the floor/ceiling joists.
Once the corners on both sides are sprayed, the remaining space in between can be filled.
I noted that this application strategy did not lead to any separation of the foam from the floor/ceiling joists, thus no small gaps.
Skill, sight and collaboration
One may assume that if you get an insulation company with a good reputation, you will not run into the above outlined quality control issues. I noted that this has less to do with the company’s reputation, but heavily relies on the skill and diligence level of the actual applicator (the guy with the spray gun) and his/her assistant (holding and dragging the hose).
Some individuals have the experience and attention to detail to provide a good product and can sustain a level focus while on the job. Others don’t.
Even if you get a good team, there will be glitches. The applicator and his/her assistant have a very hard time seeing because their full face goggles constantly get littered with spray foam. Even frequent cleaning of the goggles only partially helps.
To make things worse, bright construction lights or sunlight creates glare that makes it almost impossible to see. Even the best applicator can only do so much when operating partially blind.
I found that I am in a much better position, standing five or ten feet behind the applicator and his/her assistant. I have smaller goggles, have a clear unimpaired sight and can freely move around and look at the walls and corners from all sorts of angles. I was able to catch the missed spots in a heartbeat.
I began to tag team with the applicator and assistant, following them closely, and pointing out the spots they missed before they were too far along. But for that to work, you need a team that is willing to work with you. Those that did, appreciated my effort, because it made their work easier and faster.
… PEX tubing. I better clarify this right away before the rumor mill starts grinding…
What exactly am I talking about? We shifted modes from the potable water and drain-waste-vent (DWV) plumbing to another kind of plumbing: The PEX tubing for our hydronic heating system.
While the garden apartment has a radiant floor slab, we have planned for small baseboard radiators on the 1st and 2nd floors. A network of half inch PEX tubing connects the radiators with the manifolds in the utility room.
Each radiator will have a supply line, delivering the hot water to the radiator, and a return line, delivering the cooled water back to the buffer tank of the hydronic heating system.
The catch is that we have to do this ten times for ten rooms on 1st floor, and again ten time for ten rooms on the 2nd floor. Then, multiply this by two (for the supply and return line) and you end up with 40 runs. That is a lot of PEX tubing to handle–PEX tubing that will not cooperate unless it is carefully un-coiled.
The first task was to drill holes through the 1st floor in the utility wall. These are the connections for the PEX tubing to the manifold in the utility room below. I had to carefully line up the holes with the manifold ports.
Having learned a lesson or two from the plumbing installation, we opted to insulate the PEX tubing right away. The purpose of the insulation is twofold.
The PEX should be protected from UV light. Because the walls will be open for a while to come, the insulation protects the tubing from any light source.
The insulation also helps us to deliver the heat where we need and want it — in the radiators. Because any heat loss from the tubing occurs within the conditioned space, it may be, strictly speaking, not much of a loss. Still, we would like to maximize the system performance by effectively delivering the hot water to the radiators.
We initially looked at running the PEX tubing through the walls. That would have involved a lot of drilling through studs and way too many difficult and tight turns.
The easier route was to run the tubing under the 1st floor ceiling to each room and down the wall to the planned radiator location.
The PEX for the 2nd floor radiators is a little more straightforward and less material-intensive. The tubing also runs under the 1st floor ceiling but is then routed upwards through the floor to each room.
The simplicity of the bare bone interior suddenly disappeared. The utility wall is packed with PEX and insulation snaking all over the place.
The high tech madness continues under the ceiling with tubing spidering out into all directions. Everything begins to resemble the interior of a space craft.
Plumbing lines in conventional projects are rarely insulated. That is despite a number of good reasons to do so.
Pipe insulation will prevent condensation on the cold water lines and heat loss on the hot water lines. With that in mind, we plan to generously insulate all cold and hot water lines.
It doesn’t take much to slip the pipe insulation over the pipe sections during the installation. Remembering to do so is sometimes hard part. Once an installer is on a roll, it is easy to forget about the insulation. Ten feet of copper piping later, he either suddenly remembers, or I get to remind him.
There are small areas around the turns and connections that do not receive pipe insulation yet. We want to leave the copper tubing in these areas accessible so that we can safely solder everything together. Once the plumbing is finished and pressure tested, Cathy will again fit insulation around these spots until all tubing is nicely wrapped and covered.
There is another good reason for slipping the pipe insulation over the lines during installation.
Without pipe insulation plumbers tend to install the copper tubing right next or very close to the framing. That makes it easy to attach the pipes with brackets.
The problem is that there is no room left for pipe insulation.
If the copper tubing can’t run next to or close to the framing, wood blocks are used to attach the brackets.
Again, there is no room for pipe insulation at the wood block.
If the pipe insulation is slipped over the tubing while it is installed, these problems disappear by default.
It makes everyone’s life easier, once the ‘getting used to it’ hurdle is tackled.
The open cell foam will be sprayed on top of the closed cell foam that’s already in place, up to the back of the studs. The little gap between the studs and the oak trim is our problem. To be able to spray the foam we need to have a surface to spray against. With the gap as it is now, the foam would get all over the place, making a mess.
Because most of the pieces were not long enough, I needed to join them. I squared the short ends that I was about to join and got my dowel kit out, including the right sized drill and dowel center pins to align the dowel holes.
Once the pieces were joined together, I needed to cut them to the right length and depth. Not an easy task in an old building where hardly anything is square.
Cutting the length was actually relatively easy. But cutting it to the right depth…
My solution was to mount a strip of 5/8 inch drywall to the adjacent stud. This allowed me to hold the trim piece in place and mark where the drywall meets the trim.
I had to repeat the procedure for the other side and the trim header too. This way I was sure to cut the trim to the right depth.
The original trim was joined into one piece: The trim header was attached to the top of the sides. I took this as a clue and decided to join the trim extension the same way. To put the three pieces together, I laid them out on the floor, squared them and joined them with finishing screws.
To get a good and even connection between the original trim and the extension, I again used wood dowels.
I now could lift the extension into place. I pushed them tightly onto the wood dowels, making sure everything was straight and square, and attached the new trim to the adjacent framing with finishing screws.
The gap is plugged and another item struck of the to-do list. The next line in the list says: Plumbing. Hmm.
The Road to a Zero-Energy Home with a Sustainable Landscape
This Blog
is about how we (my wife Cathy and I) purchased a beautiful 110 year old masonry two flat in Chicago and renovate it with green building technologies. The goal is to turn it into a zero-energy home with a beautiful, sustainable and resource-efficient landscape.
