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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.

DSH Under-floor Hybrid Hydronic Heating:

General Questions


How does DSH Underfloor Heating work?

  • See the video. The solar heat is collected using large evacuated-tube solar collectors collect  huge quantities of heat during sunny days, especially during summer, but also in winter, even if temperatures are down past -30c. For this system to work the house MUST be a DSH  approved or certified energy efficient home design for the system to function as expected.
  • If not required to heat the house or hot water, the excess heat is pumped into a huge,  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 in the North Island, excluding the plateau, design is for a standard  background temp of ~18-21c (65-70f) for most of the winter.  These figures will  vary based on variables such as location, house design, thermal heat core efficiency and losses,   temperature set  point, as well as summer and winter sunshine hours (insolation). 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 suite each owner, they rarely need any other adjustments.

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, non 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 an 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 advised in colder  areas, and it can take a few years for the thermal heat core to accumulate and store enough energy             to hold the temperature 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.


There are a number of features and benefits that occur from almost free under-floor Solar Heating.

 Space & Economics

No huge ongoing and ever increasing expenses for heating for as long as you live in the home and the system operates normally. Every square metre of your home can be fully utilized: no ducts.

 Eco-Friendly, Carbon Neutral

There are virtually Zero carbon or greenhouse gas emissions during the operation of this system after the first year. As this reduces the need for external expensive oil imports, it becomes better  than carbon neutral. Think of 100% carbon offset for all you savings.

Hygiene & Health

There are huge health benefits in having warm home all winter. For example: No dust is generated  or circulated. The heating will help asthma sufferers as it reduces dust mites at floor level and can virtually eliminate toxic mould and mildew. The NZ government mandates that if you keep the house above 16.5c, mould or mildew is unlikely to grow in normal living areas in your home. No mould, no invisible allergenic spores.

 Comfort & Intrinsic Happiness

  • It is pure luxury in winter to come home to a warm home. The DSH provides comfortable background levels.
  • During the design process, care is given to concentrating primary heat in places such as bathrooms where a warm floor on bare feet can be pure luxury.

 Super Quiet

  • Compared to forced air or radiator systems, there is almost no noises, the system runs almost silently. In addition as their are no annoying drafts, dust etc is not circulated, a must for allergy  prone types.
  • The pumps are typically low power, 45-95 watt solar pump unit that is virtually silent when running.

Cost effective & Savings

  • Once installed, the DSH will typically provide a heating energy saving, from 50% to 100% over typical heating costs. The improvement when compared to bog-standard, poorly insulated existing  homes can be in the hundreds of percent. Actual results will vary and can be optimized.
  • While every system varies, it is anticipated it will cost less than $50/Yr in electrical power to operate, almost zero for systems with attached PV.

 2nd Floors

  • The DSH is designed to heat one floor which is the equivalent of the SqM (or SqFt) of the heat-store area.
  • A 2nd floor will benefit from the DSH system through conduction and convection.
  • We can increase the size of the heat storage core and install hydronic pipes into suspended a concrete floor above, to achieve the best results.
  • Remember the heat core is matched to the house footprint size, location, and circumstances of your build, meaning that the storage may not match the living areas on a 1:1 basis.
  • There is a limit to how much can be stored. As you might expect, this could result in less % of shared storage available for all floors.

Backup Heat

  • Integrated Wetback (Wood fired boiler) or other boiler heat source is simple, and only requires a few extra components as long as the pipes are in place.
  • A DC Inverter heat pump is also a good investment as it provides summer Air Conditioning as well as back up heat in winter. Note: A heat pump should be sized according to heat loss: the actual size/cost of a heat pump required is much lower in an thermally efficient home.
  • At time of ordering, these options must be considered, as the pump station changes significantly with each option.
  • A demand boiler can supply all required backup heating in colder areas.
  • A typical heat backup is either a fully automated hydronic heat pump, or a wetback/log fireplace boiler. The latter provides aesthetics of a fireplace while the DSH system is extracting as much heat energy as possible to the DSH system. We recommend a minimum of 10kW wetback/boiler.
  • We have been asked and may offer these in future.

 Ease of control

The DSH is fully automated for day to day running.

 Power Failure

The DSH system comes with a 30 minute UPS power backup system. This would account for more than  95% of all power outages.  Some power outages can be longer.

Larger batteries can be installed where power outages are expected. The UPS will slow charge these.   A standard 850CCA deep cycle truck battery may add 8 hours to operation of the system during power outages.

A backup photo-voltaic system can be purchased anytime that will run the DSH system for as long  as the sun is shining meaning the system is solar protected but will not function at night.

It is less costly to install at time of main installation

By mid 2015, new systems will be equipped with drain-back pump stations making power failures mostly immaterial. It should be noted that the solar panels normally have fluid running through them absorbing the heat energy, and regular no flow during high periods of solar insolation can decrease their life expectancy

 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


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

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