Insulating an inground endless pool
Hello All,
First post for myself. I am currently building a new house in Casper, WY and I want to put EPS (Rigid Foam Insulation) around the perimeter concrete of an Endless Pool, which will be buried about half way. The pool is 10′ x 16′ and 6′ deep in the middle and will be inside with the top being flush with finished floor. The top 3+’ will be in a crawl space and will be insulated and he bottom 3′ (about) will be in the ground.
The question I have is: Will EPS compress or degrade between the concrete and the ground (soil)? The weight of the water and concrete will be about 6 psi (3’3″ of water and 3’9″ of concrete) at it’s maximum. DOW’s EPS has a compressive strength of 25psi, which should satisfy the compression (I think), but what about the deteriation?
I have already put 2″ of EPS under the slab of the only room that has a slab in the basement. I will be putting 2″ of EPS under the garage slab and the driveway, which will have RFH/Snowmelt. I am more worried about the pool, because it should be more expensive to repair.
Thanks for any help, Woodnuck.
Replies
Seems to me the Endless Pool people would know the best way to handle this.
DanH,
They do help with reviewing your structural plans for the pool, but that is it. They really only talk about their product and recommend insulating the above ground steel frame of the vertical walls for the pool. I have their construction video, which Richard Trethewey is the interviewer. The problem is the concrete base for the pool was done and the room's floor was finished.
They erected the pool walls (metal) and then insulated between the vertical supports of the walls with EPS. I think I might have to called the EPS manufacturer and ask them if there product is recommend for it.
This applies to any pool that is to be heated: To limit the heat loss to the Earth, which is an infinite heat sink. An 80F pool won't change the ground temperature, which is about 55F. Basically it would be a geothermal well.
Woodnuck
Greetings woodnuck,
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
Parolee # 53804
Woodnuck ,
You want EXPS I beleive.
Go here :
http://www.dow.com/styrofoam/na/pro-us/products/
Or here:
http://www.foamular.com.au/pdf/foamular_physical_properties.pdf
Edited 4/7/2007 5:38 pm by dovetail97128
dovetail97128,
http://www.dow.com/styrofoam/na/pro-us/applications/slabs.htm
I found the above link, which talks about compressive strength of the RFBI. The dead load S.F. is 3 and live load S.F. is 5, after talking with a lady with DOW at their 800 #. Water would be considered live load.
Water is .433 psi/ft and concrete is 1.0 psi/ft, so I have 3'3" of water and 3'9" of concrete, which will be largest compressive strength needed. The water is 1.41 psi and concrete is 3.75 psi, multiply by their S.F. I get: Water of 7.04 psi and concrete 11.25 psi. Adding them together I need to have a product greater than 18.3 psi compressive strength.
The pool is 10' x 16' at 3'3" of water depth, with a deep middle of the pool with 8' x 12' at 6' of water depth. The concrete is 1' thick under the shallow and deep part of the pool. Between the shallow and deep part of the pool is 2'9" of concrete, so this is where the most weight is for the pool structure.
I will be putting in 2 - 2" thick of DOW's Styrofoam square edge to give a total of R-20. The pool will be at about 80 deg F or higher and the ground is about 50 deg F.
Thanks all, Woodnuck
Woodnuck, referring to an old Amoco bulletin, their AMOFOAM has a compressive strength of 41 psi (10% deflection). R is 5/in, water absorbtion .15% by volume. Their other products range from 9-12 psi.
If you're doing heat loss calcs, pay careful attention to evaporation. My understanding is that you're going to mostly be evaporating water with the heat you pay for. The cover is critical.
My indoor pool delta T to the ground is much smaller than what you're anticipating. As could yours be. I didn't bother with insulation under it (600 sq ft) as our dirt is our heating/cooling system. I'll get loss, but insignificant compared to evaporation. Which is also an air quality issue. PAHS Designer/Builder- Bury it!
Regular dow blue board is rated for more than enough to support your pool if pressure is consistant.
What I would watch out for is how the pool is built and if there are point loads that both create more psi than the foam can allow and movement that would result in tile failure, or another situation detrimental to the pool's long-term survival.
If you are concerned about point loads, it's a simple matter of pouring a weight dispersing slab over the foam.
Back in the late 80's spent a few semesters at CC. Other Wyoming towns may claim to have as much wind, but weather on Outer Drive has blown over more vehicles than anywhere but I80!
Good swimming!
Beer was created so carpenters wouldn't rule the world.
IdahoDon,
FYI, I used Warmboard throught the house except the pool room (22' x 35'). Warmboard didn't want to put their product in there. I am going to pour gypcrete in the pool room. The Warmboard sure is slick when it's wet.
The only point load for any pool would be the concrete perimeter. Concrete ways more than water (1psi/ft vs. .433psi/ft). Comparing a water bed to a refrigerator would be like comparing a pool to truck in the garage.
My refrigerator sits on four pegs, which are probably only 1 sqin in area. If it weighs 100 lbs then the compressive strength of the pegs would 25psi and 125psi with a s.f. of 5.
For a garage the point load would be the tires of vehicle. If you have a 6,000 lb truck (3/4 Ton Dodge) on 4 wheels (6"x8" of tire touching the concrete) then the compressive strength of the truck is 31.25psi. The live load s.f. of 5 would make it 156.25psi. The rebar in the concrete is to help disperse the weight of the vehicle. I was in a new house earlier this week in Ft. Collins and saw a garage ready to be poured with 2 layers of #4 rebar on 1' grids, with the second layer being offset by 6".
Outer Drive is such a short bypass that the number of turns/mi probably matches I-80 (WY portion). I live only 2 blocks from it now. It sure is calm today, I need to go outside.
Woodnuck.
I wouldn't think most pools would have any point loads, but a big fiberglass endless pool taken out of a house in Jackson was molded with heavy ribs on the underside so I figured it was worthwhile to throw in. Sounds like you're on top of it.
While the Dow blue board foam itself will handle 4100 psf, it is very easy to get an uneven surface under the foam that compresses over the high spots once loaded. This is most common when adding foam over something like road base rather than sand or pea gravel. Careful prep and it's no problem.
Did Casper Mountain really lose almost all of it's trees to some big fires the last few years?
Beer was created so carpenters wouldn't rule the world.
IdahoDon,
Before we put down the DOW square edge (RFBI) under a 4" slab, we compacted with a jumping jack and then a plate compactor. Before it was very uneven, but after it was very smooth. I was afraid of the gravel would point load the RFBI from underneath and fracture the RFBI, thus create leaks in the insulation and potentially make the concrete uneven.
The west end of Casper Mtn. was severly burned last summer. It didn't make it to Micro Road, which is where the Girl Scouts building was and other structures. I think only about 4 cabins were destroyed.
My new house looks toward Hat Six end of Casper Mtn. No sunsets, but plently of sunrises.
Woodnuck.
IdahoDon,
I just read one of your posts about building in Driggs, ID and I was wondering when having RFH (Warmboard for me) what do you suggest for the cooling side of HVAC. I was leaning towards SDHV (Unico).
Talked with an HVAC that had put in SDHV in the SE part of the country and here in Casper and he said they don't work as good at higher elevations.
I was also thinking of putting in a HRV, because I am trying to build a tight house. That way I can control the environment inside. Some others I have talked to about this are only into the RFH, not the A/C side.
Do you have any suggestions?
I posted a couple of pictures in a thread, also under EHI of the RFBI of the pool.
Thanks, Woodnuck.
he said they don't work as good at higher elevations
That's a good one. Sounds like he doesn't like installing them, rather than a significant shortcoming of high velocity units. Any hvac system will only work as well as it's design, no better, no worse.
As you know, the good thing about Warmboard is it's lack of thermal mass, and the bad thing about Warmboard is it's lack of thermal mass.
How much of a cooling load will you have? Is there a basement?
In many of the houses with in slab radiant that I've worked on at higher elevations we might as well run garden hose for duct connected to a nice shiny rock since AC was never needed due to the moderating effect of the slab.
While you don't have a slab on the main floor, you can still benefit from the mass of a basement slab by simply circulating air between floors. In situations with open floor plans and small cooling loads this can reduce or eliminate the need for AC.
If solar heat gain is the primary culprit and outdoor air temps remain relatively cool, as you probably encounter, an air exchanger can reduce your AC load by drawing out the warm air and replacing it with cool filtered outside air.
In a tight house you'll want an air exchanger anyway, so it makes sense to have it ducted so during the cold months it's also exchanging heat, but during warm months air simply bypasses the heat exchanger.
Closely related, but separate, are good performing bathroom vents. Remote fans that pull big cfm's can be very quite and since they can be operated for as long or short as you'd like, they can help to ventilate the warmer areas of the house when needed. In addition to the main timer switch located in the bathrooms, a thermostat can be wired to automatically turn the fan on when temps rise. Make up air has to enter the house, so it seems reasonable to draw it through a filter of one sort or another.
If there's an interior wall that can be poured concrete and span from dirt to upper floor, you can gain a nice chunk of self supporting thermal mass relatively easily.
Having said all that, if there is still an AC load, there are three main choices that I'd suggest.
First is a typical ducted system if framing space allows. It's the least expensive and easiest to maintain. Dedicated AC air handlers can be placed in attics and/or crawlspaces and don't have the restrictions of a full furnace.
Second is a series of ceiling or wall mounted ac units that combine cooling coils and fan in a remote controlled compact package. The new ones aren't at all like those we're used to seeing in motels and look more like an overgrown hvac grill. They're only moderately expensive if rooms are large but harder to work into a design (hide).
If for example you had a greatroom and a few upstairs rooms as the primary spaces that need to be cooled a single condenser can power three remote fan units for roughly what a normal ducted system would cost.
I wouldn't use them unless there's a way to at least partially hide the units since they still don't look as slick as a simple grill. Some can be mounted in ceilings with no more than 2x10 joists and others in 2x6 walls. If they'd simply make a small unit made for short duct runs these units could be used in many more situations.
Finally, and at roughly twice the price, are the high velocity AC units. Much of the cost is in the duct so if your house has short runs it makes more sense. Also, rather large return ducts have to be figured in. Our last project could have benefited from the small supply ducts, but the size of returns, which are quite important for AC performance, killed the cost/benefit advantage.
If you're leaning toward high velocity primarily because of the nice small vent openings, there are other options with traditional systems that are almost as good.
With either style of ducted AC, the limiting factor is hiding ductwork. Think in terms of ducts going in all directions, not simply one main trunk with straightforward branches for each room. We run ducts up walls, down walls, through, around, down, over, under, splitting large ducts in two, flex ducts, custom boxed ducts, etc. The most challenging projects can require literally days of thought and the combined insite of both framer and HVAC contractor. A contractor that does strictly remodels will be the most creative while 9 out of 10 new construction guys will just say, "you can't do that," every time something out of the ordinary would be the best solution.
Regardless, I'm a big fan of large amounts of insulation in all walls, floors, and ceilings. Nothing helps reduce hvac design requirements more.
Ask a HVAC guy and he'll suggest such-and-such model putting out xxxx btu's. Ask us and we'd have a lot of ground to cover before even calling for our HVAC guy's input. Hopefully that's a good thing. *chuckle*
Good cooling!
Beer was created so carpenters wouldn't rule the world.
As you know with Casper you need to keep the wind out. We are building a walkout basement over a crawl space. No slab due to expansive soils, so we have caissons. The HT room is on a slab (2" RFBI under slab) in the basement, thus with a 12' ceiling.
2x6 with closed cell spay foam, EIFS for the siding. The workshop and garage, which are on the SW of the home, use SIPS for exterior walls. I have been looking at Sto Guard to help seal the air infiltration.
For the slab wall, maybe the mechanical room should not be insulated and thus air could be brought out of it in the summer.
Our current home has SIPS walls and we have one window AC unit we put when it gets too hot upstairs (1000' up, 2200' down). Only one window and door on the west side of the home. We are on a crawl space with this house, because I didn't even think about a basement (2200') when I designed the home. I'll take all the blame. The only bad thing is the noise of the unit. We always open the windows at night and shut them in the morning during the summer.
By the way, I'm putting in a brewery in the basement, so I don't have it in the same room as the workshop, which is the garage right now.
I'm going to reread your comments in the morning, so hopefully I can fully understand which AC system to use.
Thanks for the help, Woodnuck
We have one project where the air handler was put up in the attic, hung off the roof framing to prevent noise transmition.
Will you have attic space? If using trusses they can be ordered with a space for the air handler built in.
Good luck!
Beer was created so carpenters wouldn't rule the world.
Here are some pictures of the insulated pool.
Woodnuck