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FAQ  (Frequently Asked Questions)

At Digital Solar Heat, we've done our best to create a Web site that anticipates and satisfies our customers' needs.  With that goal in mind, we've compiled a list of frequently asked questions. If you do not find an answer to your question here, please contact us.Wiring Diagram Ver 16

DSH Under-floor Hybrid Hydronic Heating:

General Questions

How does DSH Underfloor Heating work?

  • See the video at the bottom of the How it Works Page. Solar heat is collected using large evacuated-tube solar collectors that collect heat during sunny days, especially during summer, but also in winter, even if temperatures are down past -35c and it is sunny. For this system to work the house MUST be a reasonably energy efficient home design for the system to function as expected. There is no point heating the great outdoors.

  • If not required to heat the house or hot water, the excess heat is pumped into a huge,  low cost, in-ground thermal mass heat core storage area, located under your whole insulated slab, and surrounded on at least five  side by HDPS insulation or ICF .

  • The insulated area is huge, often the area of the footprint of the building. Over time, this  storage area becomes saturated with heat, and through conduction, permeates downwards  filling the heat containment area and below. This limited speed of conduction is what makes   the system long lasting. A long time to charge and a long time to extract heat free solar heat.

  • As required in winter, warm water is extracted first from the collectors or if installed, the log boiler,  or heat is extracted from the heat core storage, using the same heat core pipes, and circulated through a series of pipes laid in the concrete slab floors of the rooms. These pipes form a continuous balanced loop and act to create a large warm surface that will  heat the room to a comfortable background temperature.

  • Concrete slab floor temperature is limited to only a few degrees above thermostat set point temperature, with the floor temperature nominally limited to “Warm”. This is critical to eliminate slab overheating, uncomfortable floors, and only inject the nominal amount of heat  energy required, thus reducing demand on thermal storage.
  • The concrete slab is also thermal mass and once heated releases the heat slowly over long  periods of time. An isolation choice on the controller allows you to turn off the heating system, allowing all the heat to be injected into the HWC or storage as required, increasing thermal  injection and decreasing room temperatures in summer.
  • Each M2 of home to be warmed, requires ~1-3 3M of standard hard fill or hard pan or rock for  thermal storage depending upon location.
  • Expectations:
    • In optimal locations, design is for a standard  controlled background temp of ~18-22c (65-72f) for most of the winter.  These variables are designed into the system on a per customer basis.
    • The system is 'Balanced". This means the flow is calibrated on site and each leg of the  slab piping can be attenuated manually to lower room temperatures in areas where heat should be less than the living areas, such as bedrooms and laundry. Once adjusted to suit each owner, they rarely need any other adjustments.
    • For areas of N America where winters are severe, backup heat will provide a constant heat source for homes during dark days or or nights when the heat core is depleted and based on thermostatic setting(s).

Can DSH underfloor heating be installed in any new building?

  • Any  thermally efficient design with a slab floor can be considered prime candidates.
  • Note: As mentioned, it takes a full summer to get a preliminary heat charge into the thermal heat core, it can take several summers to optimally fully charge the heat core. The efficiency improves with time.

Can the DSH underfloor heating be installed in timber/wooden floors?

  • Preferably not, but yes it can, by using either heat spreader plates under the sub-floor, a baseboard heater or an air handler, none are as efficient as heating the slab and require higher operating temperatures which reduce the efficiency.
  • NOTE: The reason it is not very efficient, is mostly due to the low operating temperatures of the DSH system as well as the insulating factors of the timber and is not fully tested at this point nor recommended.

Will DSH underfloor heating affect timber flooring?

Underfloor heating will not affect wood, tile or laminate flooring due in part to the low slab  temperatures (<30c typical) which is less than most summer heat temperatures, however; be careful with natural wood flooring where moisture content must be low in the timber during  installation to prevent shrinkage. The thicker the wood the more it will insulate/isolate.

Will the DSH underfloor heating work through a carpet?

Yes however the carpet will act as a partial insulator; try to avoid thick carpets and underlays. Obviously  the system's efficiency improves without the insulating effects of a carpet system; however this can be mitigated in some areas such as bedrooms where moderate heating is preferred. Advise in the  design stage if thick or fitted carpets are anticipated as design considerations can optimize the room  heating.

Will the room be warm enough?

Yes, provided that the room meets the minimum  insulation requirements for your location, the system is operated efficiently, the system is installed correctly and reasonable care is given to  ensuring continued thermal efficiencies in the home. Remember this is not a rapid heat, but is  designed to provide a background heat over long periods. Backup heat will be required by code in colder  areas, and it can take a few years for the thermal heat core to accumulate and store enough energy  to provide heat over long periods of dark days, depending upon location.  If heat core thermal energy is depleted, backup heat kicks in to maintain temperatures.

Will the DSH floor get hot?

No, generally underfloor heating has a low return temperature and is designed and limited to few degrees above the thermostat set-point temperature. This eliminates stress in the concrete and reduces the time it takes to get up to temperature from cold. The floor gets up to an adjustable temp that is just below uncomfortable on your bare feet. The heating system is designed as a background heat. Areas can optionally be manually zone controlled.

Can I use an underfloor heating system as a cooling system?

We don't recommend it as cool air tends to stratify close to the floor, unlike heat which tends to rise  and mix. Install a quality DC Inverter Heat Pump for your best cooling option. DSH is working on a future solar A/C option.

What about a backup or Wetback?

The DSH has an option to integrate a wetback, a hydronic heat pump, or other boiler. The Digital controller will first direct incoming solar heat to the Hot Water Cylinder/Tank and house, then dump excess heat into the heat storage core. The slab, and core have preset limits built into the DSH  system.

 Off Grid Option

  • If you are considering going off-grid, an off-grid option is available.
  • It requires a PV system be installed as per normal, preferably with deep cycle batteries.


  • We try to keep the DSH costing as reasonable as possible. Example: a 200SqM (2152SqFt)  single level home will run around $75 SqM (~$7 SqFt) depending on country. To this you must  add the installation costs which typically run around ~$9.7k+.  Always get this quoted in advance.
  • Pricing on request. Best if a floor plan, and foundation plan accompany requests for pricing


See the commercial section for added insight into scaling the DSh stem up.

The DSH system is scalable. Examples of large structures that are deemed ideal: Warehouses, Shopping centers, Gymnasiums, Offices, Recreation centers [especially those with pools], Drill halls and Airports & Hangers.


Part of “Part 3 of CSA 448:”

Canada Approves Standard on Underground Thermal Energy Storage Design and Installation of Earth Energy Systems (From: Canadian Standards Association 448)

“Canada has adopted a national standard that will encourage the use of underground thermal energy storage for earth energy systems (Part 3 of CSA 448 on Design and Installation of Underground Thermal Energy Storage (UTES) for Commercial and Institutional Buildings€¯). UTES stores available energy within the subsurface of the earth ground or groundwater) for heating and cooling applications. Projects are operating in a number of countries and are the subject of an international collaboration under the Energy Conservation Through Energy Storage Implementing Agreement of the International Energy Agency. This collaboration has provided the technical basis for the new Canadian standard.

UTES (Underground Thermal Energy Storage) has significant potential for increasing energy efficiency and reducing greenhouse gas emissions from the use of conventional energy sources. Three federal government departments collaborated with the Earth Energy industry to develop the standard ā€“ Natural Resources Canada, Public Works and Government Services Canada, and Environment Canada.

UTES has been used to store large quantities of thermal energy to supply process cooling, space cooling, space heating, and ventilation air preheating, and can be used with or without heat pumps. Underground thermal energy storage is used as an energy sink and source when supply and demand for energy do not coincide. UTES may be used on a short-term or long-term basis; as the sole source of energy or as a partial storage; at a temperature useful for direct application or needing upgrade or in combination with a dehumidification system such as desiccant cooling.]”