Underfloor heating. Advice, comments, experience etc

stubot · Jun 16, 2018 11:05 pm

Hi.
I am brand new here looking for hints, tips do's, don'ts fuel sources etc...anything surrounding underfloor heating and how to go about it, I've had a quote 15,000 ( indicative ) come back for the house, basically in screed for 80sqr mtr ground floor + 2 bathrooms upstairs and radiators for the 4 rooms but I am concerned not about $$ but about how to go about this with the builder (Simonds) the sales lady wasnt much help and seemed to think i'd have to talk about this with site manager but others say NO make sure there is mention of allowance to do this heating product at construction within the contract before signing. We'd fund this ourselves off contract, meaning from our capital, not included in bank loan for various reasons but just was hoping maybe someone who'd recently done this might or otherwise have some insights. On everything from construction to legalities to floor type and warranties etc. Or just anything to add to the myriad of confusion.. I just dont want to get caught in a position where I cannot do this at all due to lack of experience and naivety thinking sales person is looking out for me and signing away on the dotted line when in fact they know very well this is my first ever home build and lack important knowledge... Thanks in advance for anyone replying with advice.
Stu

StructuralBIMGuy · Jun 17, 2018 8:24 am

stubot

Hi.
...the sales lady wasnt much help and seemed to think i'd have to talk about this with site manager....

LOL... and do what talk to the Site Manager the day before the concrete pour?
...you are dealing with builders that don't care about architectural finishes
I suggest you find another specialist custom builder

Melos · Jun 17, 2018 8:36 am

We had our included in our contract and it was part of our electrical plan. The builder needs to do the work you don’t want to subcontract it our yourself as if there are any issues the builder will blame you and warranty issues get messy

stubot · Jun 17, 2018 4:11 pm

Thanks StructuralBIMGuy. Well I've got a quote back for a full custom house design and it came back 15-20k less than some others, with the dounle garage so pretty happy and we're proceeding.
I signed my 2k away to proceed. What I think I'll do is wait for them to do all this internal office stuff, drafting etc. And will approach the heating at the next phase. Before signing a contract and get this included. Thoughts here is, they'll do all this work which costs them money so they wouldnt want to lose a customer over something like some underfloor heating. Surely not the first and wont be the last requestor. Just gotta play the game I guess.

stubot · Jun 17, 2018 4:17 pm

Thanks Melos. Could you elaborate more on what type heating you got and what or how many rooms included maybe some costs. Was this something your builder was quite happy to accept and install. If I can do the house for 15k as a central heating source I'd be stoked. Just need to figure out how to bring the quote / supplier I have already with the builder to include and co-ordinate this addition in the build.

Saint Mike · Jun 18, 2018 11:26 am

We had it in bathrooms. Not sure I'm a fan.

A good floor mat and ducted heating seems just as good - and maybe cheaper.

alexp79 · Jun 18, 2018 2:53 pm

For big areas you might be better off with hydronic in slab heating (or in screed).

In bathrooms you generally put electrical heating under tiles - it heats up much faster - you don't have to wait for days to get them heated - you can just put them on timer every morning before you wake up.

For in slab gas hydronic heating, I had a quote from DPP Hydronics of $15K for 160 sq m.
Under tile electrical heating is relatively cheap to install, i.e. only few hundred dollars per bathroom.

Also, I am not sure if the radiators upstairs will be actually needed - better invest into good insulation, your heat from downstairs will be raising up anyway.

stubot · Jun 18, 2018 10:04 pm

Thanks alexp79.
Yeah I think the Hydronic in slab is the better option and just downstairs, the wife wants the bathrooms primarily, this is how we got started and typical me getting carried away with doing the whole house. I'm willing to throw approx 15k at it for some NICE heating. Would add value to house with the idea to save $$ in the long run. The electric underfloor guys keep pushing capital costs and less complexity as why their product is better. Any idea what the builders are like when you mention some in slab hydronics. Think it might be easy to work with them on this ( Simonds)??
Thanks for the comments.
Cheers

alexp79 · Jun 18, 2018 10:07 pm

Not familiar with the project builders' reactions (custom ones are generally okay).
But keep in mind that hydronic heating in slab generally requires extra 25 mm slab height + one level up on reinforcement.
Other than that - I don't see any issues as long as your installers provide the warranty.

stubot · Jun 18, 2018 10:10 pm

Ohh and also, when might one think about approaching the builder concerning ones hopes for hydronic in slab heating. Sales wasnt that helpful but pretty confident i want this so was thinking to get them to a point they want me to sign and discuss after they do a the siting and architectural stuff.
Any advice here is really helpful
Cheers

alexp79 · Jun 18, 2018 10:18 pm

Most probably the project builders will be already having their own installers.
For custom builders, you can always discuss with them and send them quotation from the installer and then they just add it to the contract.

stubot · Jun 18, 2018 10:22 pm

So alexp79, can I ask. Did you end up getting hydronic heating in slab or other. Whats your opinion of how it operates. Any negativity in the decision. What sort of air temps would one expect etc and any other useful points. If you did go that way that is :-)

Also I asked an above a question on timing to ask builder. Whats your thought on that one.
Thanks again

alexp79 · Jun 18, 2018 10:36 pm

stubot

So alexp79, can I ask. Did you end up getting hydronic heating in slab or other. Whats your opinion of how it operates. Any negativity in the decision. What sort of air temps would one expect etc and any other useful points. If you did go that way that is :-)

Also I asked an above a question on timing to ask builder. Whats your thought on that one.
Thanks again

Nope, I have decided to fully insulate my slab instead (under slab, edges, thermal breaks where needed), put "warm" timber to the ground floor throughout, apply some insulated thermal mass here and there and just use normal reverse cycle or gas fireplace to heat up the house (which, to my understanding, may be only needed for a few days in a year), considering calculated 12 hours temperature lag (due to presence of insulated thermal mass) coupled with 21-26 temperature range throughout annual temperature fluctuations.

Still deciding if I would need some underfloor electrical heating in my bathrooms though.

With regard to the timing - better sooner than later. Definitely BEFORE they quote you.

stubot · Jun 18, 2018 11:11 pm

ok thanks again alexp79.
Re: With regard to the timing - better sooner than later. Definitely BEFORE they quote you.
One last question.So I paid 2k to submit to tender and get that process inlvolved then I guess i get final quote once architectural draftsmen and such have finalised everything is ok and they give me a contract. So you think i should speak to someone now about hydronics and if the sales lady didnt seem handy. She was advising not to ask officially, yet talk to site manager when building :-D

but this is too late and am already stuck in contract. So how might one get around sales and venture onto someone a bit more knowledgeable as to achieve my outcomes. Also, do you think if i had to because builder said no way to hydronic in slab that a smaller custom builder could offer similar price to what my estimate has been. Like within 5k max
Thanks heaps for your time, it's appreciated.

alexp79 · Jun 19, 2018 12:51 am

As I said, it will most likely require different slab design, so makes sense to discuss at least before they start structural engineering and provide you with the final quotation. You would not need this details for your council approval though, but would definitely require them on your drawings for the construction certification. If you are in NSW, very helpful for the BASIX too.

Otherwise, your construction certifier might not be very agreeable to such variation on the way.

May be you would need to speak to someone who is doing your building design and managing DA/construction certificate paper work.

Custom is generally more expensive to build than project, but a lot depends on a builder and what he is agreeable to. I have seen few exсeptions.

ddarroch · Jun 19, 2018 3:03 am

Hi OP, I was curious what sort of underfloor heating you'd be quoted for, as you have an interesting mix of requests, with radiators, & underfloor in the bathrooms & downstairs.

I certainly wouldn't be going electric underfloor for a large area downstairs, as it can be frightfully expensive to operate. It should be reserved for small floor areas, if used at all. I'd forgo it completely, unless the wife insists. In which case I'd just install it in her bathroom.

FYI, ignoring heat losses, electric underfloor heating, like most electric heat sources, is 100% efficient. Which, due to the price of electricity, makes it very expensive to operate. The only electric heat sources which are cheap to operate are heat pumps (of which reverse cycle air conditioners are a type), which are between 300-500% efficient (referred to as COP). So for every 1kW of electricity used, electric underfloor will produce 1kW of heat. While for the same 1kW of electricity a reverse cycle air conditioner will produce between 3 & 5 kW of heat, making it the cheapest of any heat source.

Also note that hydronic panels (unless super-sized) operate at a much higher temperature than hydronic underfloor. This would complicate any hydronic system that includes both panels & underfloor hydronics, increasing installation costs.

After reflecting about all this, I'd be installing split systems air conditioners upstairs. They are the cheapest to run, & will also cool bedrooms if required (though fans are much cheaper to run).

As for downstairs, if you do go underfloor heating, I wouldn't recommend installing the hydronics in the slab. You will lose some heat to the ground, particularly if the slab isn't very well insulated. But even more importantly your hydronic system would be coupled with the very high thermal mass of the slab. This results in extremely slow reaction times to changes of temperature, measured over many, many hours. This is really only recommended overseas in cold climates which require constant heating over many months. Not for 99% of Aussie climates, that have variable winter weather conditions.

So if you do go for underfloor hydronics, I'd recommend using special XPS boards above the slab. The hydronic PEX tubing is inserted into these, & then a topping screed is used. This system will not suffer heat losses to the ground, decoupling the thermal mass of the slab from the hydronics, significantly lowering the thermal mass of the overall system.

As mentioned, electric underfloor heating downstairs would be frightfully expensive to operate. Leaving either gas or a heat pump as your choice for your hydronic heat source. Gas will be cheaper to install, while a heat pump (using the same technology as AC's) will be the cheapest to operate, though expensive to install.

Yes, underfloor heating would be a very pleasant heat source (particularly for allergy sufferers). But due to the added cost, & the fact that it is far from a mature market in Australia (meaning that the quality of installers vary greatly, with some horror stories), I'd forgo the underfloor heating all together. Unless you want the best, & have the funds to throw money at what will be an expensive installation.

Personally, I'd stick to reverse cycle air conditioners in most cases, which are now the cheapest heat source. Add a nice big 6.6kW solar PV system in the roof, & you can heat the house for free while the sun is up.

alexp79 · Jun 19, 2018 2:02 pm

I am second to ddaroch here.

Consider in screen instead of in slab, insulate your slab properly (under the slab + edges).
Consider heat pump vs gas.

You don't need radiators in 2 story house - they take space, cost money, require different (more expensive) boiler and usually you do not require so much of a heat in your bedrooms - heat from the ground floor will be lifting up, anyway.

Alternatively, check out Discreet Heat - they have very elegant hydronic skirting board heat solution which you might like more - it will be significantly more efficient than raditors and in slab/in screed heating.

stubot · Jun 19, 2018 4:38 pm

Cool.
Thanks for your advice and is considered and appreciated alexp79 and ddaroch.
Just the kind of help and direction I needed..

JB1 · Jun 19, 2018 10:14 pm

alexp79

stubot

So alexp79, can I ask. Did you end up getting hydronic heating in slab or other. Whats your opinion of how it operates. Any negativity in the decision. What sort of air temps would one expect etc and any other useful points. If you did go that way that is :-)

Also I asked an above a question on timing to ask builder. Whats your thought on that one.
Thanks again

Nope, I have decided to fully insulate my slab instead (under slab, edges, thermal breaks where needed), put "warm" timber to the ground floor throughout, apply some insulated thermal mass here and there and just use normal reverse cycle or gas fireplace to heat up the house (which, to my understanding, may be only needed for a few days in a year), considering calculated 12 hours temperature lag (due to presence of insulated thermal mass) coupled with 21-26 temperature range throughout annual temperature fluctuations.

Still deciding if I would need some underfloor electrical heating in my bathrooms though.

With regard to the timing - better sooner than later. Definitely BEFORE they quote you.

Hi Alex, how are you insulating the edge of the slab?

Gaudi · Jun 19, 2018 10:35 pm

Brilliant info Ddaroch

I have electric under tile heating in bathroom
Wouldn’t install it again.
It’s cheap to run as it’s a small area and you’d only have it in short periods.

But I also have central heating ceiling vents in the bathrooms so rarely bother with it.

Reverse cycle heating / air con for upstairs is great idea......in summer upstairs is warm.
Much cheaper to run than cooling all rooms upstairs.
I’d do that next time