Radiant Cooling in Residential Construction
How and does it make sense?
Hydronic Radiant Cooling in Residential Construction is in its infancy in North America especially in Canada, but is more accepted in Europe. We are frequently asked if cooling of a home can also be achieved using the hydronic radiant heating system the home owner plans to install. While the short answer is yes, there are several factors that need to be considered. Here is an excellent post on the subject by John Sieghentaler.
In Europe lately the summers tend to be much hotter. Natural land coverings like grass and trees are replaced with concrete an asphalt which retain and build up heat a lot more. Other natural changes exacerbated by humanity raising daily high temperatures during summer to dangerous levels.
In North America these changes are also present but in Canada summers are much shorter and winters are usually brutally cold. The cooling season is much shorter and A/C is only really needed for 2-3 months out of the year.
In Europe energy costs a lot more than in North America therefore the return on the investment one makes in radiant heating and cooling is much faster there.
Purpose of home building
In Europe most single dwelling homes are built to be occupied for a long time by the same person. Families build houses they will inhabit for generations especially in southern countries like Italy, Spain, Greece and Portugal. Installing the best possible heating and cooling system makes sense as the person building them will enjoy the benefits and savings they offer. In Germany people don’t bother to buy homes, 50% of the population rents. Cost of utilities are most often than not are not included in the rent. If you want to rent your property out you better have energy saving setups in place or you will have to offer them at a discount. This incentivises the population to save on energy costs by any means possible.
In North America many houses are built to flip as an investment for the lowest cost possible. People are hesitant to install a radiant heating and cooling system that costs $30,000.00 only to be able to sell the home for $10,000.00 more because of it. The return on the investment of such system will not be enjoyed by those installing them as energy costs are much less than in Europe.
How will I save money using hydronic cooling?
There are several different methods (see below) of cooling the water to be used for radiant chilled water cooling in the home. Each of the methods will bring about different ways of energy savings. In every instance savings are realized by using a lot less electricity moving water around with energy saving circulator pumps than it would cost moving air using large fans. The need for large ducts is either eliminated or largely reduced.
Technology and material
Visiting the largest water and energy show in the world the ISH in Frankfurt, you will find dozens of products and manufacturers geared towards hydronic radiant cooling. Ceiling panels from Enetec offering complete radiant ceiling panel systems help complete and safe state of the art installation. Nobody carries their products in North America. GeoCollect Geothermal Panels that make collecting geothermal energy simple; don’t exist in North America. Importing these goods from Europe is prohibitively expensive for a homeowner. It is very frustrating for the HVAC professional to be aware of these solutions but unable to get his hands on them. The answer to this problem is education. Educating the HVAC professional and homeowner alike and raise awareness in these technologies.
There are many ways to use radiant cooling in a home. We can use ceiling panels to cool the ceiling or walls, we can use the existing radiant heated floors to circulate cold water in the summer, we can use hydronic air handlers in traditional forced air systems to heat or cool the home.
Each have their unique issues to keep in mind and engineer for. Condensation is the #1 issue. Surfaces that are colder than the given dew point for any relative humidity will have condensation forming on them. If it is on the ceiling you will have indoor rain and mold. If on the floor you may slip and fall. If inside the ducts it may come out all over the place. On supply and return tubing, the same thing.
While condensation is not caused by radiant cooling the contractor installing it will be blamed for it. Advanced controls are needed with resets for relative humidity to prevent condensation on cooling surfaces, the cooled surface should not be lower than 66F. Humid air must be vented, condensation forced to take place in areas designed for it (inside HRVs, on A-coils, in air handlers with drip trays under them). All this planning, proper install and controls will not help if on a humid day someone leaves the door or window wide open. Care must be taken to mitigate damage from condensation if such even should occur.
Aptitude and attitude
Very few HVAC professionals in North America have ever installed hydronic cooling. They have nowhere to go to learn the practical challenges of installing such a system. Accessible support in design doesn’t exist. They will not go out on a limb and wing hydronic radiant cooling in a client’s house because of the legal and financial liabilities if their ideas don’t work out. Many of these HVAC professionals simply lack the motivation to get into this field because there is no competition forcing them to widen their scope. Our goal must be to upset this comfortable apple cart. The latent demand is there. Education of professionals, supporting them with help and designs that make practical sense will help grow this nascent field.
Government – Code and Regulation
While more Government is rarely the solution to any problems, it is indisputable that subsidies and code requirements helped radiant cooling and heating get off the ground in Europe. Providing incentives for the builder and home owner to use renewables, mandating they properly insulate their dwellings, offer tax breaks for importation and sales of radiant and geothermal equipment would speed up the proliferation of hydronics. While people usually want to do the “right thing” for the environment it is foolish to ask them to pay 4x for the “green” solution over the not so green one. The free market will take care of this once the green solution is jump started. Once the technologies of geothermal, radiant cooling and heating, heat pumps and solar gets adopted across the field prices of these systems will drop dramatically because of improvements in manufacturing and savings through competition. Subsidies can then be removed freeing tax payers from the burden of bankrolling the green revolution.
With all that being said
Ways to implement hydronic radiant cooling in residential construction
What can be cooled with chilled water?
Water is 3,500 times better at conveying heat than air. A given volume of water can store 3,500 times the heat than the same volume of air when they both undergo the same change in temperature. Basically a 3/4″ diameter tubing can transfer the same amount of heat than a 20″ x 12″ air duct. The cold water in the tubing can cool:
A Hydronic Air Handler A-Coil
A Water Chilled Recessed Ceiling Panel
A Radiant Ceiling Panel
A Water Chilled Fan Coil
A Water Chilled Wall Mounted Fan Coil
Water chilling methods
There are several ways to cool water to be used for hydronic radiant cooling. They all offer varying amounts of savings over traditional methods.
Water at the bottom of any lakes in Canada tend to be the same temperature all throughout the year. This temperature difference between the bottom and the surface can be extracted. For cooling all we need is a stainless steel water to water heat exchanger in which the heat of the air from a house can be exchanged to that of the cold water in the lake. This of course requires piping to the bottom of the lake complete with strainers and filters to prevent sediment and critters from plugging up the heat exchanger. There maybe permits required for such a system. The return water to the lake is discharged to near the surface or maybe used for other purposes. The cost of running the system is the cost of electricity to run the circulator pumps and electronics. A fraction of cooling that air down by traditional methods.
Ground source heat pump
Similar to a lake or any other large body of water, temperatures below a certain depth in ground tend to be stable all throughout the year. This heat can be extracted and used in ground source (water to water) reversible heat pumps to heat or cool water as needed. The cost savings come from the efficiency of a heat pump. The smaller the ground and target heating/cooling temperature difference the better.
Air to water heat pump
As mentioned above heat pumps operate by exploiting the temperature difference between where the heat pump is placed and of the space they need to heat/cool. Below 20F air to water heat pumps offer no savings over a strictly electrical heater. The optimal heat pump temperature range is 25-30 degrees Fahrenheit and up. Water cooled using electricity during off-peak hours can be stored for use later in insulated buffer tanks.
Air cooled condenser
In systems using air cooled condensers from a traditional air conditioner setup, the cooled and liquid gas cools water or a mixture of water/propylene glycol through the walls of a stainless steel flat plate heat exchanger. This cooled water then is stored then used in insulated buffer tanks. The cost savings come from the water cooled using electricity during off-peak hours.
Finding Qualified HVAC Professionals Who Can Do The Work
When looking for an HVAC professional to install any hydronic radiant heating or cooling system the most important factor to consider is their competency. It is imperative that you as a builder or home owner educate yourself on the type of system you are looking to have installed. Only when you know what is what can you then ask pointed questions about the proposed system. If the installer gives you clearly wrong or evasive answers you need to keep looking. Always ask to see pictures of past similar systems he installed and ask to contact those clients of his. If you contacted them ask how well the system is working and their level of satisfaction with the installer. We at Hydronics.com recommend only those who meet our stringent criteria for being able to deliver a quality product and service. You can start your search for an installer on our Authorized Service Providers page.