akpolaris
Well-known member
So if I put radiant heat in a cement floor and lose power to keep the water heated for an extended period of time and the water freezes what happens? To manage that risk can glycol be used in that system?? Thanks
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Radiant heat loops freezing??
- Thread starter akpolaris
- Start date
soapii
Well-known member
That's the idea behind using glycol, as far as I know.
x2 Similar to geothermal heat systems.
--Joe
Highbeam
Well-known member
But what would actually happen? The pex is supposed to be quite resistant to damage from freeze. The valves, boiler, pumps, etc. are not.
mygarageone
Well-known member
But what would actually happen? The pex is supposed to be quite resistant to damage from freeze. The valves, boiler, pumps, etc. are not.
Well let's put it this way ice exerts 2000# per sq inch , something will most like give .
Why take the chance.
rlitman
Well-known member
PEX can expand without cracking in the event that the water in it freezes, probably through many (but not an infinite) number of cycles. But once the water forms a freeze plug, you cannot turn the heat on, because you will get no flow. And then the rest of the system (as said, valves, pumps, boiler) all fail when everything freezes.
There are issues with using glycol in a system connected to an automatic filler that comes from a drinking water supply. You need to be careful that the potable water is not contaminated (there are ways to deal with this safely). Just pointing this out.
Also, glycol carries less heat, and is a less efficient heat transfer material than pure water. This probably won't affect you that much, but it is something to take into consideration.
There are issues with using glycol in a system connected to an automatic filler that comes from a drinking water supply. You need to be careful that the potable water is not contaminated (there are ways to deal with this safely). Just pointing this out.
Also, glycol carries less heat, and is a less efficient heat transfer material than pure water. This probably won't affect you that much, but it is something to take into consideration.
So this requires a system completely separated form the domestic water. Once frozen the pex system would have to be unfrozen with the surrounding environment. The domestic stuff buried in the walls would be easier to manage the that pex buried in the cement. Sounds like a generator is necessary.
rlitman
Well-known member
Completely separated is an option (and not an awful one on a closed loop system).
A reduced pressure backflow prevention valve might be sufficient too.
A reduced pressure backflow prevention valve might be sufficient too.
BadgerBoilerMN
Well-known member
When water is frozen in PEX tubing encased in a slab the unavoidable air pockets that form around the PEX pipe allow the PEX to push out into the void. The result is like that of a leather punch.
The appropriate mix of propylene glycol, backup generator or battery driven pump to keep the water circulating in a blackout would be advisable.
The mix should be as week as possible since, as rlit suggests propylene glycol will derate the efficiency of heat transfer and the pump.
The appropriate mix of propylene glycol, backup generator or battery driven pump to keep the water circulating in a blackout would be advisable.
The mix should be as week as possible since, as rlit suggests propylene glycol will derate the efficiency of heat transfer and the pump.
APEowner
Well-known member
I would think that with the pex in the slab that there would be danger of cracking the slab if the water froze.
pseudorealityx
Well-known member
The % of glycol, either Propylene or Ethylene is easily found based on your required temperature range. While you obviously don't want to add more than you need to because it will lower the efficiency of the heat exchange, it's still a lot less costly than having to replace bumps, pipes, boilers, etc.
skidoo
Member
So is it advisable to use distilled water with a mix of propylene glycol?
I was thinking a 70/30 mix (30% glycol) or 60/40 at the strongest. Temps here are rarely below -25c, and my hope is that the slab will retain some heat for at least 2 or 3 days
I was thinking a 70/30 mix (30% glycol) or 60/40 at the strongest. Temps here are rarely below -25c, and my hope is that the slab will retain some heat for at least 2 or 3 days
Wouldn't radiant floor heat in a garage be a bad idea since you are effectively heating the earth?
In a house, like in the 1st floor flooring, heat transfer can go any direction as heat absorbed by the basement air will rise, making it insignificant. In a radiant floor thats directly attached to the earth, heat doesn't really rise when its transfered through solid surfaces, atleast not that I know of. It would seem to me that the earth would be absorbing a small but significant pecentage of that heat, enough to make it a poor option atleast.
Also, having a high thermal mass in a space which is not used for living space would seem like a poor option as it will cost an arm and a leg to get up to temp. All that money would be heating that place while your sleeping. You heated up that slab only to not need it.
In a house, like in the 1st floor flooring, heat transfer can go any direction as heat absorbed by the basement air will rise, making it insignificant. In a radiant floor thats directly attached to the earth, heat doesn't really rise when its transfered through solid surfaces, atleast not that I know of. It would seem to me that the earth would be absorbing a small but significant pecentage of that heat, enough to make it a poor option atleast.
Also, having a high thermal mass in a space which is not used for living space would seem like a poor option as it will cost an arm and a leg to get up to temp. All that money would be heating that place while your sleeping. You heated up that slab only to not need it.
Randy in Maine
Well-known member
That is why we use at least 2" of rigid foam under the poured concrete slab, colder climate guys sometimes use 4" to give us a good thermal break between the heated floor and the cold earth. Our goal here is to just heat the slab so we also install a thermal break between the heated slab and the stem wall foundation also. I have 21 cubic yards of 4000 psi 6" concrete in mine which is about 42 tons of thermal mass. No source of ignition in the garage as the hot water comes in from the house. Once the slab is warm, it stays warm with little additional heat added to it. It takes 1 hour to heat the building 1º F. I turn it on at Thanksgiving and off in April.
I keep the garage at 55º F (air temp 4' up the wall) which is very comfortable and cost effective. The floor is about 5º warmer than that.
I keep the house at 65º F (air temp 4' up the wall) with radiant floor heat in the wooden floor with foil and R-19 insulation under it in the crawlspace. The floor is about 5º warmer than that.
I am into pretty good insulation foam in the house and my garage is made of SIPs. Money well spent.
I heat 1200 square feet of house and 1200 square feet of garage with a propane fired Baxi Boiler that gives domestic hot water. Water goes out at about 115º and returns at about 90º. I also have a gas kitchen stove. I go through about 600 gallons of propane a year x $2.49 a gallon. Not bad in my book. Better than any of my neighbors with no garage.
I keep the garage at 55º F (air temp 4' up the wall) which is very comfortable and cost effective. The floor is about 5º warmer than that.
I keep the house at 65º F (air temp 4' up the wall) with radiant floor heat in the wooden floor with foil and R-19 insulation under it in the crawlspace. The floor is about 5º warmer than that.
I am into pretty good insulation foam in the house and my garage is made of SIPs. Money well spent.
I heat 1200 square feet of house and 1200 square feet of garage with a propane fired Baxi Boiler that gives domestic hot water. Water goes out at about 115º and returns at about 90º. I also have a gas kitchen stove. I go through about 600 gallons of propane a year x $2.49 a gallon. Not bad in my book. Better than any of my neighbors with no garage.
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That is why we use at least 2" of rigid foam under the poured concrete slab, colder climate guys sometimes use 4" to give us a good thermal break between the heated floor and the cold earth. Our goal here is to just heat the slab so we also install a thermal break between the heated slab and the stem wall foundation also. I have 21 cubic yards of 4000 psi 6" concrete in mine which is about 42 tons of thermal mass. No source of ignition in the garage as the hot water comes in from the house. Once the slab is warm, it stays warm with little additional heat added to it. It takes 1 hour to heat the building 1º F. I turn it on at Thanksgiving and off in April.
I keep the garage at 55º F (air temp 4' up the wall) which is very comfortable and cost effective. The floor is about 5º warmer than that.
I keep the house at 65º F (air temp 4' up the wall) with radiant floor heat in the wooden floor with foil and R-19 insulation under it in the crawlspace. The floor is about 5º warmer than that.
I am into pretty good insulation foam in the house and my garage is made of SIPs. Money well spent.
I heat 1200 square feet of house and 1200 square feet of garage with a propane fired Baxi Boiler that gives domestic hot water. Water goes out at about 115º and returns at about 90º. I also have a gas kitchen stove. I go through about 600 gallons of propane a year x $2.49 a gallon. Not bad in my book. Better than any of my neighbors with no garage.
Ah, the foam, that makes sense.
But at the same time, thermal mass doesnt really save money, it just means you dont have the option to turn it off and on when you're using it. It saves money in a house because your house takes all day to heat up in the summer and then your AC gets to operate at night time, which is not during peak hours and is generally cooler.
I thought the only reason radiant floor heat was energy efficient was because it allowed for lower boiler temps, which is more efficient. But I can appreciate the lack of an open flame.
Definitely has its benefits, but I dont think its really saving any money. Probably more expensive since it is running all winter. The slab staying warm for a long time doesnt really decrease fuel usage from any other method of heating.
Randy in Maine
Well-known member
But my 2 VW 1979 camper buses as well as all of my tools and my woodshop all stay about 55º all winter with no temperature fluctuations. Radiant floor heat is great if you are painting or building engines as there is no dust.
The part that saves money is that I am not heating up a building from 0º-30º F (which is about what it is for most of the winter here outside) I am just keeping it at 55º. I am also not heating up water to 180º to send out to a radiator, I am just adding about 30º to the same water before I send it back out to the garage or to the house. Heating air would be worse as there would be a lot more temperature spikes. Nobody here in Maine really uses a forced hot air funace unless they are using mini-splits or they have an old system or don't have a choice. I am in it for the long haul and figure energy only gets more expensive down the road.
I am not sure how long it would stay warm if the power went down as we rarely lose it (even in Superstorm Sandy), but I would problably take a long time before I would have to worry about the pex tubing freezing. I could run the boiler off a generator or a car battery and inverter if I had to I suppose.
The part that saves money is that I am not heating up a building from 0º-30º F (which is about what it is for most of the winter here outside) I am just keeping it at 55º. I am also not heating up water to 180º to send out to a radiator, I am just adding about 30º to the same water before I send it back out to the garage or to the house. Heating air would be worse as there would be a lot more temperature spikes. Nobody here in Maine really uses a forced hot air funace unless they are using mini-splits or they have an old system or don't have a choice. I am in it for the long haul and figure energy only gets more expensive down the road.
I am not sure how long it would stay warm if the power went down as we rarely lose it (even in Superstorm Sandy), but I would problably take a long time before I would have to worry about the pex tubing freezing. I could run the boiler off a generator or a car battery and inverter if I had to I suppose.
BadgerBoilerMN
Well-known member
Ah, the foam, that makes sense.
But at the same time, thermal mass doesnt really save money, it just means you dont have the option to turn it off and on when you're using it. It saves money in a house because your house takes all day to heat up in the summer and then your AC gets to operate at night time, which is not during peak hours and is generally cooler.
I thought the only reason radiant floor heat was energy efficient was because it allowed for lower boiler temps, which is more efficient. But I can appreciate the lack of an open flame.
Definitely has its benefits, but I dont think its really saving any money. Probably more expensive since it is running all winter. The slab staying warm for a long time doesnt really decrease fuel usage from any other method of heating.
On the contrary, a radiant cuts down convection and thereby the losses by infiltration/fenestration. Most radiant panels raise the mean radiant temperature making the room feel warmer at lower ambient (thermostat) temperature.
You want any heating system to closely match the heat loss, like cruise control, the steady state firing of most fuel burning appliances improves combustion efficiency and the constant running of pumps improves distribution efficiency.
It is true that thermal mass has little to do with efficiency unless the mass is being used to store heat in an off-peak, solid fuel or solar application.
BadgerBoilerMN
Well-known member
Wouldn't radiant floor heat in a garage be a bad idea since you are effectively heating the earth?
In a house, like in the 1st floor flooring, heat transfer can go any direction as heat absorbed by the basement air will rise, making it insignificant. In a radiant floor thats directly attached to the earth, heat doesn't really rise when its transfered through solid surfaces, atleast not that I know of. It would seem to me that the earth would be absorbing a small but significant pecentage of that heat, enough to make it a poor option atleast.
Also, having a high thermal mass in a space which is not used for living space would seem like a poor option as it will cost an arm and a leg to get up to temp. All that money would be heating that place while your sleeping. You heated up that slab only to not need it.
Straight from the dark ages...
The typical soil acts as an insulator and is wind-proof. The heat loads in an un-insulated basement are 1/3 of the main level and the same level on an insulated slab is 1/3 of that number.
If you travel to the southwest you will find every other home on a radiated slab.
We installed over a million fee of polybutylene over bare ground in for commercial buildings only insulating the perimeter for the frost.