Topic: heating design

heating design 

Hi we are currently designing a two storey house and wish to use an air flow heat pump to run underfloor heating on the ground floor and radiators on the 1st floor.We have been advised this cannot really be done.We also need to think about incorporating our hot water into this system.Any advice or ideas,contacts would be greatly welcomed and appreciated.
Cheers

Re: heating design 

why cant if be done?

The only issue i'd see from underfloor, radiators and domestic hotwater is that the first two require a lower temp the the HWC, but an electric booster in the HWC would sort that.

Re: heating design 

Hi Jimmy,

Your biggest issue is the water temperature required for the radiators. Most require water temperatures well above what a heat pump can produce which is generally around 60 degrees where a traditional radiator will require 70 deg plus.

One option is to look at low temperature radiators such as those produced by Jaga ex Belgium which will operate on 40 deg water. They are fan forced and move air around more than a traditional radiator though.

Re: heating design 

Jimmy,
Do you need radiators?
If you're still at the design stage then design for maximum insulation. The cost you would have incurred for a radiator system can be used to beef up the insulation levels, windows.
We're currently under construction with our house and are having UFH in the concrete slab for background heating with a wood burner for when it gets cold. The upstairs (bedrooms+bathroom) will have no heating at all, we are hoping that the heat percolating up in addition to R5+ walls and ceilings will make it unnecessary.

have a look at http://picasaweb.google.com/lansdownescouts/ConstructionPhotos# if you want to see what we're doing.

Pete

Re: heating design 

Hi Pete,

I just had a look through your construction photos - nice looking house!

I am about to start building my own home and am putting UFH in the concrete slab like you. I noticed in some of your shots there are portions of the piping that seemed to be sheathed in something.

What is the sheath and what areas are you protecting? I am aware you need to be careful not to run the piping under any walls as nails/bolts used to fix the bottom plates will puncture the pipes. And we also need to try and avoid running pipes under the proposed slab cuts, but is there anything else I should be aware of?

Finally, what are you using to drive your UFH? Air-to-water HP?

Regards,
Ben

Re: heating design 

Hi Ben,
Thank you for the compliment.

Yes you are correct about slab areas that you should avoid. I sheathed using 25mm conduit that I bought from Mastertrade.

Firstly, I sheathed 200mm either side of a slab cut. If there were to be any differential movement either side of the cut then I'm hoping the conduit will take up the slack rather than the UFH pipe itself. Not sure if this is over the top but the belt and braces approach gives me piece of mind. I also sheathed in an area where the pipes needed to cross a slab thickening (unavoidably), as we were not allowed to insulate in this load bearing area.
Finally, the flow pipes running down the hall were sheathed in an attempt to lessen the heat flow into this part of the building (these pipes go to a granny flat on the western end of the building). The returns from the granny flat are unsheathed as I don't mind any residual heat being given up here.

Hope this helps, best wishes for your own build.

Pete

Re: heating design 

Forgot to add :)
Yes I am looking at using an air to water HP as the heat source for the UFH.
Long and low heat rather than quick and high. The house has R5.5 walls and also two Woodburners so hopefully the idea of the UFH is to keep the background heat from dropping below about 18C.
Pete

Re: heating design 

Thanks for that reply Pete.

So your sheathing was more to protect from any strain on the UFH piping if/when the slab cracks, and to reduce heat loss down the hallway?

Is it a plastic sheathing? I.e. it is not going to protect anything if a bolt or nail is put in the wrong place? You are just relying on not laying any pipes under walls to avoid this (obviously I guess!)?

Initially I thought the sheathing might have been something more solid, but this all makes sense now.

I am hoping to only need the UFH for my home but will have a gas fire in the main living area in case I need a boost, and for ambiance.

Thanks again for your reply.
Ben

Re: heating design 

When installing the pipework for infloor heating it is very importent this is done by a suitably experianced person and if possible check their previous work and visit a working home.Most companies would have a good client that would accomodate such a request.If they haven't they probably havent been round long enough and do you want to be their learning job??

In answer to your question. Yes you need to avoid the bottom plate fixing anchors .I find no need for sheathing apart from at the exit point of the pipes from the floor slab to provide flexibility of pipe movement for manifold connection.
The entire system is drawn out prior to installation(I use a computer pipe fitting program) and this gives a entire pipe layout based on the house plan and where walls are.Also ensures you have calculatd that circuits dont exceeed the maximum pipe length.It is importent you have signed off on wall placements as these should not be altered later for obvious reasons.
When the foundation is ready for the pipes to be laid,I get the builder (make him responsible) to mark All Walls,shower pans,permanent fixtures in spray paint onto the foundation.I then lay the pipe as per my original plan.
By this method all floor fixings will not be close tothe pipe andI've thankfully never had a pipe penetrated through the slab.

It is Importent way the circuits are laid as there are different patterns and centres for different areas and using the appopriate fixings and spacings.I learnt just this week of another company in town that installed a hydronic floor and when the floor was ground for polishing the pipe was just below the surface in 5 spots and a major fix is underway.
I believe this came about due to the radius bends lifting(In experianced installers I bet)
Other issues with penetration are in the robustness of the underfloor insulation,with a day of walking around on the slab laying pipes or laying concrete the mesh way tilt and box a little so allow a little more on instals with high mesh chairs but no need on systems like cupolex.(best in my opinion).

I take a camera full of photos at high resolution as I have on fairly regular occasions had plumbers ask for permission to move their pipe normally by small amounts.If I can see in the photo it is clear space they can go ahead.This is easy to spot as the mesh gives you a grid line and scale.If it is too close it is tough luck for the plumber my infloor doesn't get touched!
I also put the systems under working pressure at time of laying and get the builder to sign that this is so.Any leaks or pressure loss is now at their cost.The builder is damn careful from this point on and if in doubt would ring me rather than pay a repair bill(Repairs are possible but a real pain to do)

Best Heating source depends on more factors than I can go into but suffice to say you should base it on lifecycle costing and price of energy in your area,Some places with NG can do it effectively with a condensing boiler,Farmers may use diesel and town folk heat pumps.All have their pros and cons.

Recently installed the Daikin 16kW altherma HWHP system and it's impressive worth investigating as it has its own HWC and does the infloor and Domestic hotwater thanks to a three way valve and the outdoor unit is amazingly quet but the 300sm home we put it in is toasty and HWC has never run out.

Had good results from gas systems too lower capital cost but less features or controls and not as many energy suppliers.

If you have the money the very best system we can do is to double height the bottom internal frame plates and lay the pipe after the internal walls are installed(Eg European method).we use an insulation mat then plastic staple the pipe to the mat.This is finished with a runny screed that gives a perfect floor finish and the pipes are nearer the surface so quicker response time(More energy efficient).Will be double the price for laying the pipe due to the insulation material,more screed and you ne

Re: heating design 

Hi RG

Is there a trade name for the insulation mat?

You mentioned the cupolex system and I had a look at their NZ website - do you add the heating pipes on top of the mesh, which is on top of the plastic moulds, and then pour a thicker layer of concrete as opposed to the 40mm noted in all the drawings shown on their website?

Seeker

Re: heating design 

Hi Seeker,

Yes increase the cover to 50mm generally(but not always) the OD of the heating pipe is 16mm so that still brings the pipework close enough to the surface that it has a quick heating time and also has adequete level of protection.

Tacker sheets available from Rehau ltd in Auckland.
Hope that helps

RG

Re: heating design 

While I remember the advantages of Cupolex from a Hydronic point of view is a really high R vlue of R2.6 thanks to the trapped air and that it is robust to walk on especially early in the day before the sun warms the black plastic.