Hydronic Heat

This came in from someone who unfortunately, was never a client of mine.  The problem boils down to lack of proper hydronic heating design…

I had radiant floor heat put in my new home (2850SF) in Oklahoma City. It is run by propane. The propane tank was installed in Sept 2008. I moved in during Jan 2009. Since then (12 months), I have blown through 3000+ gallons of propane! The gas people are blaming the floor heat and the floor heat folks are blaming the propane company. I’m at a loss as to where to go next. I’ve spent more than $8000 for propane since last Jan. Can you give me any advice?

There are a few possible reasons:

1)     The structure/poor insulation or excessive infiltration – you may want to have a local HVAC or mechanical contractor perform an energy audit to see if your structure has infiltration or insulation issues.

2)     Heat source inefficiencies – for systems I design and sell, I typically recommend the heat source be set up and fired off by a local pro – where applicable, a combustion analysis should be performed on gas and propane-fired heat sources to insure they are operating within manufacturer tolerances and at peak efficiency.

3)     System installation issues – depending on your system design, there may be issues with the amount of tubing, spacing of tubing, water temperatures, water flow rates, floor coverings with high r-values.

Bottom line – it sounds like your system is working hard to keep your structure at temperature – and it sounds like it’s working.  (You don’t mention being uncomfortable or cold) – your home loses “x” amount of BTU’s per hour – and your system needs to put out “x” amount of BTU’s per hour to keep up.

If it’s fighting poor insulation or thick floor coverings – well, that makes it the structure, not the system.

If it’s inefficiency at the heat source – a local pro should be able to test and adjust for that.

If it’s a design/installation issue – there may be some things you can adjust like water temp and flow rate…and some other things that would be less practical to go back and change – like amount and spacing of tubing.

Bottom line – it sounds like this could have been either avoided or explained to you by a competent radiant heat designer.  Hopefully, you’ll be able to use these answers as talking points with your local contractor – hope you can get your radiant system working better soon!

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Step 3: Analyze your project requirements – determine your project needs and address any initial concerns:

To properly analyze your hydronic heat project requirements you’ll need to know or be able to provide the following information – or your supplier will need to be able to figure it out for you.

Heat Load Estimate – Heat Source Sizing

To insure that your radiant floor heat system will do the job – your system needs to be designed to put out more BTU’s per hour than your structure can lose.  There are a few different ways to approach a heat loss estimate.  Sometimes the architect does one as part of the floor plan – you may need to look to a mechanical engineer or your radiant system designer.

Factors that come into play include the climate at your construction site – insulation values for walls, ceilings, windows and doors – and domestic hot water usage.

Hydronic Heating Installation Methods Include:

* Tubing installed in a concrete slab on grade
* Tubing installed in a topping slab
* Tubing installed in a thin-slab on Subfloor
* Tubing attached below a Subfloor
* Tubing attached with heat transfer plates below a Subfloor
* Engineered Subfloor with metal and tubing grooves
* Above-floor boards with metal and grooves
* Lumber overlay method with or without plates

See our “radiant basics” category page for a brief overview of these methods.

Your radiant heat system design will need to take into account the method by which your tubing will be installed.  In some cases, more than one method will work, and that means you and your system designer will have to decide which methods are right for your project.

Tubing Spacing

This will be determined by the heat loss estimate and your method of tubing installation.  Some suppliers will provide you with a customized tubing layout with spacing and loop length guidelines.  This can be an invaluable service to a first-time radiant installer and opens the door for novice do-it-yourselfers to install their own radiant system – and get it right the first time.

Operating Temperature

This will be affected by all of the above factors.  Your system designer should be able to give you the design temperature range for your system.  In some cases, further tweaking may be necessary once your system is up and running.

Fuel Type

You have several options: Natural Gas, Oil, Propane, Electric, Wood, Solar, Waste Oil, Bio-Diesel and a few other alternatives.  Your choice of heat sources may be determined by the type of fuel choices available at your site.

Zoning

Your system designer should be able to make zoning recommendations for you based on your plans.  If you have specific zoning requirements, let your designer know – they’re usually happy to accomodate those requests.

You may need custom radiant system design work and system submittal documentation – this will be important when it comes to your permit applications and sometimes your energy code/Title 24 paperwork as well.

If you’d like me to take a look at your hydronic heat project and provide an estimate, feel free to contact me through the contact form above…

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hydronic heat16″ height=”162″ />In a hydronic heat staple-up system the radiant piping is attached to the underside of the sub floor by way of staples, j-hooks or metal plates. Insulation is recommended, but not always necessary.

A good rule of thumb would be 3-4 times the r-value below the tubing as above. R-values are cumulative, so if you have a sub floor with floor coverings that have a cumulative r-value of 3 – you should have at least r-9 to r-12 below your radiant tubing.

Staple-up systems may need to run at a higher temperature, it will depend on your radiant designer.

This method is often used in retrofits where joists are accessible as well as many new construction project. The benefits to this hydronic heat installation method are a low materials cost – it is however a more labor intensive installation.

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