What is the CLIMAWIN Window system and how does it work ?
Climawin is a high performance window with an integrated preheating (ie heat recovery) ventilation function. It is essentially two windows in one (a double window) and heat escaping through the inner window is picked up by external air being drawn in through the gap allowing it arrive into the interior room preheated (ie having recovered the heat being lost from the room through the inner glass layer.)
The system has automatic ventilation valves which regulates air flow according to sensors (detecting interior temperature humidity or CO2 levels) mounted remotely within the room (and communicating wirelessly with the window).
What’s special about Climawin ?
As well as being high performance in purely thermal insulation terms, they are a ventilation system. Not only that, they perform as (the key part of)1 a heat recovery ventilation system, and a passive, healthy one at that.
What do they cost ?
While each situation must be priced individually, Climawin is cost competitive, especially when compared to high quality (passive) windows and when one considers it is also a ventilation system.
How do Climawin windows compare to other windows ?
Climawin is far more than a window so one would need to compare them to the combination of a window (whether passive or not) and ventilation system to get a fair comparison.
When compared to a mechanical heat recovery ventilation system (HRV or MHRV)1 Climawin has many benefits for the same result: less maintenance (changing of filters, cleaning of ducts), easier controls and less noise and vibration than a PW - MHRV combination.
Cost wise, Climawin windows would be comparable to high performance or passive windows but given they include much of the heat recovery functions of an MHRV system, they will be favourable when compared to these two technologies which are both typically installed in a high performance or energy efficient house.
What controls the ventilation and are room sensors needed ?
Climawin’s valves automatically adjust to allow more or less air in depending on the internal conditions of the room. Its sensors, which are installed in most rooms, detect temperature and CO2 levels and compare these to outside levels (measure at the window face) and adjust to allow
air in as necessary. The sensors are a standard part that is proprietary to Climawin and are
mounted on the ceiling in the centre of the room with no wiring being necessary. Once a number
of rooms have been fitted, a zone controller is also installed (again without wiring).
How does Climawin comply with building regulation ventilation requirements ?
Climawin windows have a bypass valve as well as a number of heating (or cooling) vents. These
in combination with the central extraction system would allow Climawin conform with the natural
ventilation with mechanical extraction approach to Part F of the Building Regulations; the bypass
or heating/cooling valves serving as general (inlet) ventilators while purge ventilation is
addressed by ensuring that the Climwain version installed allows both glazing leafs be fully
Does Climawin count as a renewable energy device ?
No, Climawin recovers heat being lost from the system and recycles it. It does not create any
How is a Climawin system powered and does installation require an electrician ?
There are 3 available options for Climawin in regards to power; a low cost semi automatic
version that requires no power, an automatic version that is autonomous (using small PV panels
and batteries) and a recently developed fully integrated (ie wired) 110/220v option. Only the last
requires an electrical installation and connection to the buildings power system.
How Does Climawin Perform Save heat and energy ?
Most windows lose as much as 6 times the heat as the wall in which they sit and only Climawin
can reuse that lost heat to become a pre heating solution – passively. Climawin in an Irish or UK
climate performs as a passive heat recovery system. It captures the conduction heat being lost
through its inner glazing layer and uses it to warm the incoming air. In warmer months Climawin
can reduce incoming air temperatures too.
In hotter locations, Climawin, with integrated blinds, can produce energy savings by allowing
daylight in (but preventing unwanted warm air coming with it) so reducing electrical (lighting)
What else is required to make the system work ?
Climawin relies on air being drawn through them toward the inside of the house. In most places
the stale air in homes is mechanically extracted centrally (in the bathrooms and kitchen) and this
is sufficient to draw air in through Climawins valves. Where such extraction systems are not
present, Climawin would be installed in tandem with off-the-shelf devices (eg from Aereco or
Renson) that can create this extraction very efficiently. The most recent version of Climawin can
remotely activate the central extraction systems when the room sensors tell Climawin that interior
air conditions require fresh air be supplied.
There is also the potential to add a heat recovery (air or water) device to the central air extraction
system to recycle that lost heat back into the homes hot water system for increased energy
Are there parts which need maintenance or replacement ?
Climawin requires little maintenance once installed.
The individual leafs of glazing open to allow the space in between be cleaned. Since there are no
ducts (the rooms themselves convey the air) and no filters, maintenance associated with theses
elements (cleaning, changing) is eliminated .
On the non wired option, batteries could in exceptional circumstances become exhausted and a
simple manual recharge (similar to recharging a phone) can be performed. During such a period
the windows will work as a trickle vent for safety reasons.
What is the difference between a Climawin system and Passive Windows ?
The high performance aspect of passive window (PWs) is that they reduce the heat loss through
the windows themselves significantly. However they still lose heat (the best passive window still
loses at least 3 times the heat of an average wall) – and need a separate ventilation system
(whether one that recovers its heat or not). In addition passive windows only achieve the
advertised energy improvements if the entire house has been designed and constructed to the
Passive House standard whereas Climawin achieves its improvements by just installing new
Climawin windows are close in U Value (thermal insulation performance) to PWs but in addition
to this they work as a ventilation system that actually raises the temperature of the air coming in
Climawin is capable of supplying 52% of the heat required to adjust the incoming fresh air to a
comfortable temperature, on all facades (and up to 92% on southern facades).
Overall (ie for the whole building across the whole year) this results in the previously referenced
24% (for Ireland) energy savings – achieved by just changing the windows !
Have the windows been tested and what were the results ?
From 2010 to 2014 Climawin was designed, simulated and tested by the prestigious Fraunhofer
Institute in their field test centre at Holskirchen and in their Laboratories at Stuttgart. Early
designs for Climawin were studied and researched at the Engineering Department of Aalborg
University, Denmark (specialists in low energy facades), Denmark.
Their studies predicted that a typical Irish house fitted with the Climawin system alone will reduce
its annual energy bill by 20% to 24% while providing comfortable (temperature and humidity
wise) fresh air to occupants. The methods used complied with EN/ISO 13790 (1) and were done
in 3 ways (computer model, building lab, and in a real field test house). The reference house
was a 2 storey pitched roof home of 140 sqm area, with 10 windows (each 1.48m(h) x 1.23m(w)),
4 facing south, 1 north and 5 east/ west. U values are assumed as following; W = 0.28, roof= 0.2,
windows (before)= 1.01 and door 1.8 (all W/msqK). Airflow through the Climawin was assumed
to be 4 Pascals (about 3.6litres/sec through Climawins vents) and an air change rate of 0.4 ac/h
was the assumed target for the house. It was assumed that the occupants desired an internal
temperature of 20 deg C, that normal heating and ventilation devices/regimes were operating
and scientifically accepted typical climate days in Dublin (it was also done for Copenhagen) were
taken to represent the external temperature and conditions.
The Climawin glazing arrangement (a number are possible) was the variation shown to produce
optimal results; a layer of double glazing externally, an air space (where a blind can be fitted) and
a single glazed layer facing the interior. Various coatings and fills are applied to different
surfaces/cavities within this assemblage.
This house was estimated to use 16,571kW/yr putting it on the borderline between a DEAP B2
and B3 rating in Ireland. The average house in Ireland is much worse than this.
The studies and trials showed that simply fitting Climawin to this better than average Irish house
would reduce its annual energy demand to 13261 ie a saving of 19.9%. Other versions of the
tests and models indicated it could be as much as 24%. These test of course also take into
account energy required to cool the buildings in warm months.
They also showed that even on an overcast day or where walls face other than south, Climawin
can recover 57% of the heat needed to make outside air comfortable (20 deg C) on its way
in. This rises on a south facing condition to be meet 100% of the air heating needs and can even
become a net energy gain in sunny conditions – where Climawins bypass and cooling functions
could be utilised. In terms of air temperature increase, on a overcast winter day the tests showed
that incoming air could be increased in temperature by 11.5 degrees and on a sunny day (even
in winter) by 20 degrees celcius plus.
Have real life tests been carried out ?
Yes, between 2015 and 2017, six pilots were installed across Europe and tested for up to 24
months each. The results confirmed the predictions above and showed that Climawin can
improve comfort (increase the temperatures of incoming fresh air for ventilation in Winter and
reduce it in summer) at lower energy costs than with other heat recovery ventilation approaches.
Can Blinds be integrated into Climawin ?
Yes automatic blinds can be accommodated in the gap and provide important energy (daylight
emittance) enhancement in warmer seasons or hotter climates.
Are there any situations where Climawin may not be suitable ?
In general the wider the Climawin window the more air can be drawn though the system, while
the higher the window the more heat recovery occurs. There may thus be situations where a high
density of occupants combined with limited external wall space may mean Climawin is not an
What are the Climawins materials and U values
Climawin comes in Alu clad, solid wood and wood composite.
Static U values are in the range: 0.79 to 1.00 W/m2K approximately
However this measurement does not properly capture the energy benefits that installing the
Climawin system provides.
Do all windows in a house have to be Climawin ?
No, typically only one Climawin window is required for each habitable room. That means in larger
rooms not all windows need to be Climawin and for non habitable spaces, corridors, staircases or
stores conventional windows will suffice.