Imbedded radiant heat longevity
Whether “in” or “out”, expensive or not, I’d like to know what others think about electric or hydronics’ in-floor heating longevity.
I’m a layperson, but imbedding PEX or mats into concrete seems risky given that many warranties are 20 -25 years, (even if lifespans of material are much longer). What do you do when a portion fails/leaks? Do you need to rip up your colored concrete floor?
Note – If the conversation was attaching mats to the underside of a floor (from basement), I wouldn’t be writing this, but imbedding in concrete just seems like it isn’t worth it. Am I missing something? Home should be around for hundreds of years, and concrete isn’t like ripping our sheetrock.
Thank you.
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Replies
What’s the motivation for building a home that lasts for hundreds of years?
It’s a frequently debated topic !
It takes so much time, energy, and money to build, I did not think it was a topic of debate. What is the main reason(s) cited that builder's shouldn't? (higher upfront cost?)
I see home built in the 1850's that owners are still remodeling, so my assumption is that a home built with the building science we have today should be able to get even better longevity, and designed in a way that better facilitates future remodeling.
Cost, unpredictability, energy (concrete is long lasting but terrible for the environment currently), etc.
There are some 200 year old houses out there. There are many more that aren’t. Most people today wouldn’t choose to build or live in a house from the 1800s.
I don’t think modern building science necessarily means house will last longer, just that they are more efficient and comfortable. There are structures still around from the Roman Empire, they just aren’t super comfortable to live in (or maybe in some environments they are…)
Exactly. Who cares if your house can last 200 years if it’s somewhere no one wants to live? Conversely, who cares if your house can last 200 year if it’s somewhere a whole lot of people want to live? Predicting out a century or two is wildly difficult!
Paul,
Yeah, the longevity of houses - and whole communities - is largely dependent on demographic and economic factors, not the way they are constructed. Houses and places people want to live in get maintained and renovated.
That said, it makes sense to me to build a way that encourages and makes it easy to alter a dwelling over time. To me that speaks of making things like desmising walls and equipment easier to move and replace, rather than trying to make everything last centuries.
For the most part houses get torn down because they're no longer needed or are otherwise functionally obsolete, rather than because they're worn out.
So building houses out of more durable materials is actually wasteful.
“ What do you do when a portion fails/leaks? ”
Stop using it? Then you’re in the same stop as if you didn’t install it? But that probably won’t happen, even long after that warranty. I can’t imagine a company warrantying anything longer than 30 years….
freyr_design,
"Stop using it? Then you’re in the same stop as if you didn’t install it?"
Except you have designed your house around that heat source.
I agree. Warranties aren't a good proxy for longevity. And anyway they rarely cover anything but the replacement value of what was installed, not the ancillary expenses due to damage. Look at shingle warranties. They aren't worth the paper they are printed on.
I guess my main point was; is it unreasonable to think you might have to fully overhaul your hvac system in 50-60 years? The chances are there will be some new, better way of conditioning our spaces, especially if we are thinking 100-200 years out. It won’t hurt anything to have the radiant sitting in your slab.
Look at houses from the 1800, non of them were heated with heat pumps…. Maybe we will have some fusion device that heats each room that’s the size of a cup.
I think the biggest drawback to slab radiant is adding/ modifying plumbing is substantially more complicated.
freyr_design,
Interesting timing. I was just looking at photos of the circa 1910 Montreal townhouse I grew up in, and notice they have added mini-splits to it while retaining the original radiators, which may still be in use, or are just there as architectural elements.
https://www.realtyhop.com/building/529-avenue-lansdowne-westmount-qc-h3y-2v4/townhouse/3295484
I've been pondering a similar issue the last few days, the life span of the system and its repairability. I've come to the conclusion that, as attractive as the idea may be from an economic efficiency perspective, putting the piping in the slab has serious disadvantages for someone building for the very long term. I see a few options and I've attached an image that helps illustrate.
1. Structural slab as finished floor surface - piping in slab. Problematic on a number of points. It's been my experience that using the concrete slab as the final finish is a headache throughout the entire construction sequence, because of the protection measures that must be put in place so that it still looks pristine after all the construction is done. If various spaces are to have different floor finishes (tile in a bath, hardwood in a bedroom...) it makes the transitions awkward. And then there's the longevity issue you mentioned.
2. Piping above slab. There are a number of ways to do this depending on your desired final result.
2a. What I show in the image on the right would allow for a variety of finish flooring surfaces. Warmboard makes their "R" board, which is thinner than their structural sheet. Convenient. Allows for complete repairability with the loss of only the lightweight finish flooring. That's probably the best it gets as far as getting at the piping. This arrangement also avoids having the piping having to heat up the concrete slab, which allows the system to respond more quickly. Another advantage is in terms of construction sequencing, since all vapor barrier, slab, insulation and finish flooring could all be done much later. The only possible drawback is that it puts the slab outside the thermal envelop, which is only an issue if one is designing a passive solar system where the mass is needed inside the house. That's not often done these days and if necessary one could still put the insulation below the vapor barrier, as I show in the left detail.
2b. Either of the options I've shown would work with a non-structural topping slab instead of the Warmboard. It's routine to put piping in a topping slab of about 1 1/2" thickness. This would give the opportunity to still have the appearance of a finished concrete slab but would have the following advantages. The piping could be repaired without having to break into the main slab. Yes, the topping slab would be affected. But there's no way around damaging any finish floor if you're doing a slab on grade. Also we get the same thermal mass benefit of not having to heat up the main slab.
Of course all these options are going to be more expensive up front, compared to putting the piping in the slab. But the advantages may well be worth it. I will be doing something along the lines of the right hand option in the image, in 2-3 years, when I intend to build myself a new house.
I grew up in a house with copper in the floor for radiant heat. Many houses in that development started losing tubes in 10 years.
I don't think barrier pex has a lifespan that most would consider problematic. It is more likely that shifts in the concrete lead to leaks. Which kind of means your finish floor looks like crap already.
Otherwise it is early failure from damage during install.
Dig up the spot. Fix.
Now you need a new floor finish.
Or an area rug....
In general when mechanical systems are installed there isn't a lot of thought given to replacing them at the end of their lives.
In the 20th century, millions of houses were built with galvanized steel plumbing that only lasts about 30 years and requires large-scale interior disruption of the house to replace. Millions of houses were built with knob-and-tube wiring, which generally functions as well as it did when it was installed, but is usually discarded because the modern alternatives work so much better, and again requires interior demolition and rebuilding to retrofit.
Twenty years ago many houses were prewired with telephone, ethernet and cable TV, which is essentially obsolete now.
In the 19th century virtually all houses were built without indoor plumbing, electricity or gas. Those things had to be retrofitted, and in some cases it was deemed not worth doing.
Let's back up and ask three more basic questions:
1. Is concrete a good residential flooring material?
No, it's terrible. It's hard and uncomfortable. As other have noted, it's easily damaged and impossible to repair completely. Concrete is terrible for the environment and its use should be minimized.
2. Are heated floors a good way of heating house?
Only minimally. The heat output of a radiating surface is determined entirely by the temperature difference between the surface and the air in the room. Floors have a narrow band of temperatures where they give the desired effect -- below about 80F the warming isn't noticeable, above 90F it starts becoming uncomfortable to stand on. In most of the US you'll want cooling anyway, so install a heat pump for cooling. If you want the heated floor effect, size your floor so that it can stay between 80 and 90 all winter, and so that your heat pump can make up the difference when the floor heat isn't sufficient.
3. If you decide to have a heated floor, is concrete a good material for it? No. You want any kind of radiator to have as little heat capacity as possible, so that it responds as quickly as possible to any changes in the heating load and thermostat setting. That maximizes comfort. Concrete has more heat capacity than other alternatives and thus provides worse comfort. As noted above, concrete is also to be minimized for environmental reasons.
If doing an entire house in radiant floor heating I would choose Warmboard and install Steller removable wood floors throughout most of the rooms and tile in the bathrooms and mudroom.
https://www.warmboard.com/
https://floorsbysteller.com/
However, for a much more responsive heating system (one that is able to quickly heat a room as well as provide cooling) I would install minisplits and put an electric heat matt under the tile.
rockies63,
Someone needs to invent the equivalent of the Stellar system for tile.
That is a pretty slick floor system. I appreciate all the comments in the thread.
I have a similar setup, where I have an air to water heat pump that provides hot water. I have heated floors in the bathroom and air handlers that provide heat when the floors aren't enough and cooling.
Here's the thing about doing it with electric matt: for maximum comfort, you want to set it up so that the floors are on almost all the time in the heating season. And if you do that, the floor ends up providing the lion's share of the heat. If the floor is powered by electrical resistance, you end up with a system where most of your heat is being provided by resistance, and the heat pump only comes on when it's pretty cold outside -- which is pretty much the opposite of the way you want to use a heat pump for maximum efficiency.