Best way to solve this insulation problem
Our master BR is over our garage and has had a couple of pipes freeze over the years. With the recent sub zero weather they all froze and during thawing (A torpedo heater in the garage) one of the pipes burst.
I have torn out everything and can see how it was done now. There is 40 feet of pipe that runs into the space.There is a heat duct that goes into the area on the side furthest from the exterior wall. They had R19 batts in the ceiling hangers which are just a couple of inches below the floor joists.
So main problems, the heat duct was pointed at the cold air resturn 4 feet away so the air would go straight to it, I added additional duct to get it to the other side where the pipes that froze more often were.
Air infiltration, I have been sealing big gaps with can foam and I have a spray foam kit that I am going to use to seal up everything including the bottom of the BR floor.
My problem is sealing up the bottom (Which is the ceiling of the garage) it is basically a tiny room from the bottom of the BR floor to the top of the ceiling is about 15 inches. When they put the batts in they stuck up past the 2×4 ceiling hangers and would touch the floor joist above so there would be no air flow through the area from the heat duct. I want to leave room between the cieling hangers and the floor joist so the warm air can circulate. The cieling hangers are 24 inch apart.
The problem is that does not give me much room for inulation. My ideas so far are:
1) Put 2 stacked 2″ rigid foam boards in between the hangers for an R20 value. Con is the cutting and fitting and getting it sealed well, plus it will reduce the space for air flow about an inch.
2) Put a smaller 1″ foam board at the top of the hangers and spray foam the cavity using the foam board as the backstop for the spray foam. Cons – getting the spray foam even, plus the cost but this would give me R 19 and should be well sealed from air leakage.
3) Again use the smaller 1″ foam board and seal the edges with can foam and then put 3 1/2″ inch R13 batts in the cavity. This only gives me an R18 but would be better air sealed than the R19 they had in there before.
So do any of these ideas sound OK or is there another option I should go for?
In addition to the above I have already put foam pipe insulation around all of the pipes for an additional layer of insulation within the cavity. Basically I am trying to create an envelope around the tiny room top sides and bottom to keep out cold air, keep in the warm air and protect the pipes. Hopefully it will aslo help the BR floor stay warmer as well.
Replies
When a pipe is run in a wall/floor/ceiling that separates warm and cold, never put insulation AROUND the pipe -- put the insulation on the cold side and leave the warm side of the pipe uninsulated.
The pipes are in a conditioned space
There was not enough heated air to overcome the cold air coming into it though, coupled with the lack of air flow from the insulation that was there before. I understand what you are saying but even if I only insulated the garage ceiling I would still have the issue stated above. How do I insulate the ceiling but still allow for good airflow from the duct and stop air coming in.
BR subfloor
--------------------------------------------------------------------------------------------------------| Spray foam bottom of floor
O heat duct | joist | oo Pipes| | | 000 Pipes | Wall inside the garage roof line
| Garage ceiling hangers | | | Spray foam perimiter joists
Need to insulate here between these hangers
the foam pipe insulation...
...that scott is referring to is made to fit around pipes and is intended for use on pipes wherever they are located for a couple of reasons.
First is to help prevent freezing pipes in unconditioned spaces, which is what Scott has described.
A second very common use of the foam pipe insulation is in basements and crawl spaces around the cold water pipes to help prevent condensation dripping during high humidity conditions in those areas like what you might have during summertime.
be very meticulous installing the foam pipe insulation scott!
Somewhat confused....
The assumption in your stated goal of creating air circulation in the insulated space below your bedroom floor is at odds with the dynamics of using fiberglass insulation or any type of insulation. You want to eliminate air movement, not encourage it. Air moving over and through fiberglass insulation reduces its R-value considerably.
Your goal should be to put the thermal envelope on the cold side of the pipes. That is, you want the pipes between the heated space and your insulation. Spraying foam on the underside of your BR floor defeats this purpose and places your pipes in an area where they be colder, not warmer. Also, if your ductwork is leaking warm air under the BR floor, it should be taped up with foil-faced butyl duct tape or mastic.
Here in New England, the R-value requirement for floor is R-30. If this is your case, your best bet is R-15 between the garage ceiling joists, 2" of Thermax (R-13), 1/2" Thermax (R-3.3) taping the joints, followed up with 1/2" sheetrock, skim coated or tape & joint compound. The sheetrock is the minimum IRC fire-rated assembly for dwelling/garage separation. Adjust the Thermax (or styrofoam) for your zone requirements. Recommendation:
1- Fiberglass is notoriously difficult to install properly without leaving air gaps. The stated R-value is under perfect testing conditions. Rarely do installers or even homeowner take the time to install fiberglass to lab specs.
I have had much better luck with Roxul, an expanded mineral wool product. It is cut oversized for 16" or 24" o.c. bays. It is installed by compressing it slightly from edge-to-edge and tucking it into the stud bay where it holds itself in place without need of stapling or wires. Working around pipes, wires, outlets, etc., is simply a matter of using serrated knife (bread knife works great) and cutting the insulation like a cake. This leaves virtually no gaps for air movement / leakage.
2- Cut pieces of Roxul into rectanges and place against the rim joist above the ceiling joists (the BR floor joists).
3- You've already foamed any access holes; just check to be sure there are no other points of air infiltration. A smoke pen is ideal for this purpose (or a infrared thermometer now that they have dropped in price so much...). Caulk any leaky joints as found. Leave the foam pipe insulation on all piping.
3- Remove any fiberglass insulation and insert the Roxul into place in the garage ceiling joists. R-15 @ 3 1/2".
4- Install Thermax or styrofoam. In addition to its R-value contribution, it creates a thermal break, preventing the ceiling joists from pulling heat from the warm side. Tape all joints, including around the perimeter (or caulk the perimeter). Rooms over garages should receive particular attention in terms of air sealing due to the CO potential. Contrary to some beliefts, carbon monoxide has approximately the same density as air and tends to move with air currents (as in, it moves with the air leaks).
5 - Sheetrock and finish as desired.
You would now have your piping inside the thermal envelope, well protected from freezing. If the garage walls are accessible, insulating them is always a good idea, creating a warmer-than-outside zone under the BR.
Some may quibble with the lack of a water vapor. If that is of concern, staple and tape plastic under your BR floor joists before insulating the garage ceiling. In practice, water vapor moves much more readily by air leakage than by diffusion. By sealing up the celing under your BR, you have considerably reduced the air leakage. To be of any concern, water vapor must have a cold surface on which to condense. Good insulation does not present the required cold surface.
Best of luck.
Thank you for the response. The confusion when I talked about airflow was not about airflow from outside into the space (Although I want to stop that as well) it is the airflow from the duct. I am not talking about a duct that just passes through the space (Although there is one that runs up to the BR) There is a duct that was purposely run into the space in order to provide heat for that space, not warm air from a leak but an intentional duct run into the space to provide heat to it..
However with the size of the insulation thay had used it blocked the warm air from circulating into the space as it should have. The pipes that froze most often were the furthest away from the heating duct for the space. So in order to allow the warm air that is supposed to circulate in the area I don't want to go more than an inch above the ceiling joists.
I think at this point my best bet is to put rigid foam at the top of the 2x4 joists and then fill the cavity with spray foam which would give me 3 1/12 inches of closed cell foam.
I will look at your other suggestions and see if they will work, but like I said I need to let the warm air that is pumped into the space circulate properly to keep the space warm.
Thanks for the clarification
Ok, the picture is a clearer now. As described, you have a what amounts to a crawl space under the BR floor and above the garage ceiling. A heating duct is routed into this space to keep it warm, presumably with two purposes: prevent the pipes from freezing and making the BR floor less cold than it might be otherwise.
As ductwork is mentioned, I'll make the assumption you have forced hot air for heating. btw- does the thermostat controlling the BR temp also control the duct into the "crawl space"? (also, if you use the ductwork for a/c, is cold air dumped into this space during the cooling season?)
Sounds like DanH and I are providing very similar solutions. As you have extended the ductwork to terminate near the pipes, that area will remain warmer (provided you don't lose power!). As long as your return duct matches the deilvery in terms of cfm capacity, you will get air circulation. After all, the fan is pushing warm air into this "crawl space". After it is sealed up with your foam and caulking efforts, the air has to go somewhere. The pressure will build up and the relief point is the return duct. The air near the return duct will be pushed out of the space first, replaced by air nearby. As this process continues, the warm air becomes distributed in the space (albeit warmer near the exit point but that is the case with all heat sources but radiant).
By pushing warm air into the space, you shouldn't have to worry about air circulation. As long as there are some spaces for the air to move out of the bay where the duct dumps the warm air, you're fine. Provided, that is, the air has no where else to go, as in leaking into the garage or outside the building envelope... If you were relying on convection currents to circulate the warm air, it would be a different story.
Last, I would argue the pipes should be insulated, contrary to the recommendation from DanH. My reasoning follows (and I have no problem with being educated to the contrary).
It would seem the pipes do not have to be warmed, only kept from freezing. Street or well water, due to the depth of the water mains, comes in year round within a fairly narrow temperature band, well above the freezing point. Under normal operating conditions, the temperature in the crawl space will be maintained at a point preventing the pipes from freezing. In this zone, pipe insulation has two positives: 1) prevents condensation on the cold water pipes (which may drip onto the insulation / ceiling below), and 2) minimizes the wait time at the faucet / shower for water to reach the desired temperature, hot or cold (and saving some water as well).
During abnormally cold weather, as the temperature around the pipes drops below the temperature of the water inside the pipes, the heat, as DanH points out, will flow from warm to cold. That is, the water in uninsulated pipes will become colder much faster than if they were insulated. Pipe insulation provides a measure of security by slowing this heat transfer, possibly just long enough for temps to rise and eliminate the freezing threat. Of course, if temperatures remain well below freezing long enough, no amount of insulation will prevent freeze-ups.
On balance, insulating the pipes seems to be a net positive.
that is a really great...
..description of a best case situation that 3125995 has described-but its difficult and very expensive to achieve.
Its also not necessary for this situation.
You could blow the cavity above the garage ceilng/below the bedroom floor full with cellulose and probably get the results you want and then some-and this will be much less costly and time consuming.
You wont have any more freezing pipes!
Central Ohio
It has not been this cold since we have lived here, this winter the coldest so far has been -10, then with the windchill it has been - 30. The pipes had frozen in the past when it was in the teens and windy but we put on a new garage door last summer and he got the weather seal a lot tighter so the pipes were fine when it hit the teens. However of course it dipped into the negative digits.
Being windy made a difference in the past whether they froze or not, which is why I wanted to spray foam at least the perimter joists to keep the air out. I was thinking about foaming the BR floor for 3 reasons. One they get cold, two since the space below the bathroom is heated the heat would tend to travel up and not stay in the space, and three to reduce the volume of the space that the duct has to heat.
My thougt was if I insulate and airseal the top (Under theBR floor) and the sides and then seal the bottom the best I can and insulate then the space would stay warmer.
I am torn between 3 options now.
1) Rigid foam like I mentioned before and then spray foam the cavity between the joist. This would give me about 3 inches of foam and around an R 19 which is what was there before but with a better air seal (Assuming I can get the foam applied evenly.
2) Rigid foam and use the mineral wool insulation as suggested above, easier to do and would give me an R 20, a little better than before and if I can seal the edges of the foam well should have less air infiltration.
3) Put 2 x 2's on the bottom of the 2x4's for a little extra space. Probably the better solution but then makes finishing it back off like before a bit harder because the ceiling would not match anymore so I would have to finagle the sheetrock.
Are you planning to heat this space warmer than the bedroom? If not, insulating the BR floor will not help keep this space warm -- heat flows from warm to cold.
And the volume that has to be heated is irrelevant -- what counts is the surface area/R-value (and any air leakage).
I can't see what limitations you may be working with, but in the simplest case I'd be inclined to strip the garage "ceiling" down to the 2x4 suspended joists you apparently have, fasten about 3" of foam across the bottoms of the joists, and then cover with two layers of drywall (for fire safety). I think with up to 3" you could manage without having to add strapping to support the drywall -- more than that and you'd need the strapping.
And DO NOT separately insulate the pipes.
can you explain...
...what you mean by "the volume that has to be heated is irrelevant" dan?
Depending upon the clear span of the 2 x 4 ceiling joists I think you had best reconsider the addition of any kind of support for them such as strapping.
This is particularly important if you do plan on putting up a code specified 1 hour fire barrier with 2 layers of Type x 5/8" drywall-which is quite heavy!
Can you explain what you mean by "the volume that has to be heated is irrelevant" dan?
It seems to me that it's pretty clear, but if I have to spell it out...
Conductive heat loss occurs across a surface and is proportional to the inverse of the R value multiplied times the area. The enclosed volume does not figure into the equation.
By including this ceiling area in the heated area that is "the room", the only increase in square footage is the area around the sides, so the increase in heat loss is small.
the area around the sides??
Re -read the original post...he says the space being discussed is about 15" high. That is not an irrelevant or a small additional area that you should be ignoring.
And what's the unimpressive mumbo jumbo you copied from your text book about conductive heat loss dan?
we aren't talking about controlled laboratory conditions here-we are in a garage ceiling!
Are you willing to ignore convective heat transfer here Dan?
I am surprised because you made a rather informed comment earlier in this stream of posts to the effect that "heat flows to cold".
Seems to me that most people don't know about that simple fact-but you sure do!
Now can you formulate the adjustment to your definition of conductive heat loss that would be introduced as soon as air begins flowing in this space above the garage ceiling as the original poster said it does?
I'd like to see that formula dan....please!
Yes everything is on the same thermostat, not zoned at all so when the furnace kicks on it goes to everything (Yes forced air). Yes it would put cold air into the space in the summer from the AC, I can shut the damper in the basement during the summer to keep it from putting too much in there, however those dampers are not perfect so some cold air will get in there.
I had to get it finished since we were getting severe cold again. I ended up going with the 1 inch rigid foam between the ceiling joists and then filling the rest of the space with 2 1/12 inches of the closed cell spray foam. so in total 3 1/12 incheses of foam for an R value of around 21 which is better than the previous R 19 fiberglass before in addition to the air sealing I get from it which it didn't have before.
I turned off the heater I had going yesterday while I was working (A big torpedo heater) since I had to have the right temp to spray the foam. Overnight it got down to 5 degrees and -10 with the windchill. No frozen pipe so far but we are supposed to have negative temps for the next 4 - 5 days so this will be a good test.
I do have 2 radiant heaters in the garage, the square kind that mounts to the wall, just to try to keep the garage a little more comfortable if I am doing something in there. They don't really heat the garage that well so I wonder if they are even worth having. I do know the garage ceiling isn't insulated (The ceiling that isn't under the bathroom). is it worth it to try to insulate it?
The walls are all insulated so I was thinking if I did insulate the ceiling as well even if it only gives me an extra 5 degree difference that would be nice. I would have to put baffeles in for the soffet vents and I thought just putting batts into the ceiling joists. Not worried so much about the cost but if I go to the effort to do it would it give me any extra in the garage.
Get a cheap remote-reading
Get a cheap "indoor/outdoor" thermometer and stick the sensor in what you guess to be the coldest spot near a pipe. Put the display outside somewhere. Then you can keep an eye on it.
Good idea on the themometer
I have one in the garage right now that I bought the other day. First day since I finished and it was 5 degrees most of the morning and windy so windchill was - 12. No freezing and in the past they would have if we had not let the water run in the faucets. So doing well so far. The real test will be early next week when the temp is supposed to get to -10 on Tuesday plus whatever the windchill will be.
I may actually put some extra heat in the garage that night just to be safe.
Scott
Where do you live, NW Ohio?
I'm talking about puttng a thermometer inside your insulated floor/ceiling/whateveritis to measure the temp in there.
Great job Scott!
Using the sprayed on closed cell polyurethane foam insulation puts you where you want to be!
The air sealing accomplished with this material, if properly installed, can't be beat.
You shouldn't have to worry about the freezing pipes again in that space.
One thing you mentioned here is in regard to the ambient outside air temp of 5 degrees and a windchill of -10 degrees.
Keep in mind that while a windchill factor like that will cool things down rapidly and induce additional negative pressure upon a structure that will cause some problems with more rapid heat loss and drafts, the lowest temp that any material will get to when exposed to that windchill will be 5 degrees-except for warm blooded creatures like you and me and fido!
So everything is done and we had 2 days of sub zero weather a few days after I finished it, -10 for a low and high of 6 degrees (Windchills in the - 20 to - 30 range) and nothing froze. Also we noticed a big difference in the temp of the BR floor. So I would say it was a success since in the past at least one pipe would freeze when it was in the teens or single digits.
great news scott!
i hope you were able to glean at least some beneficial ideas from these posts-some were rigt on some were not.
you had 10 below wit a soft wind (5-7mph?) producing 20 to 30 below windchills?
that wind really isnt tat powerful and i hope your new insulation and air sealing job will withstand higher winds while you experience sub zero lows.
remember though that the air temp is still 10 below when you experience any amount of windchill!
NOAA wind chill charts are designed to reflect the cooling effect of the wind at a temperature upon the human body-but all warm blooded animals are certainlt affected by the wind chill values.
glad to hear you seem to have achieved what you wanted to!