is the nibe fighter systems cost effective?

[djh]

There is a German building standard which says 7 litres of heating oil/ 6m3 of natural gas (70kWh) per year per m2 of floor area.

There's another German building standard that says 15 kWh/m2  which is more appropriate for modern eco-houses.

Part of the motivation to develop Passivhaus was to understand why houses built to previous German standards failed to perform when built, just as British ones still do.

[rhys]

I would argue that the thermal mass on the underflooor negates the need for weather compensation, as the floor doesn't have a snowballs chance (pun intended) of reacting in time.

I have to agree though, that ASHPs are the "in thing" at the moment, but basically wholly unsuitable to most domestic applications, GSHP have their place, but again they are being mercilessly (and ill-advisedly) sold into any four walls by unscrupulous sales men who have little or no understanding of building design and thermal performance.

Useful posts here which explain weather compensation - my understanding has always been that by learning the reponse time of the building to differing internal and external temperatures and by varying the flow temperature,  they are a "good thing" especially with UFH and particulary UFH with a heat pump. Like any other building "mass" heavy walls etc. UFH has a reponse time.
http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=189

[dhaslam]

Weather compensation doesn't achieve much when you are using an air to water heat pump.   If anything the  flow temperature needs to be reduced in cold weather to avoid  inefficient running.   

[rhys]

Well I always understood thats was the point, and why for example an Ecodan air to WAter has a weather compensation controller pretty much as standard, so that the flow temperature is reduced where possible. Longer running at a lower temperature?
Loads about this here
http://ecodanlive.mitsubishielectric.co.uk/pdf/ecodan%20quick%20start%20manual.pdf

[martin]

Which in the context of the original question is somewhat akin to "can we tweak the settings to get better mpg out of the Hummer?".............
the answer being to ditch the Hummer.............