Thanks for the comment, sorry for the slow reply. You're right that radiators should effectively circulate warm air on their own by drawing in cool air, acceler

Thanks for the comment, sorry for the slow reply. You're right that radiators should effectively circulate warm air on their own by drawing in cool air, accelerating it up with a chimney effect and then expelling the warmth out into the room via a warm buoyant plume and so set up a cyclic convection current in the room. This should cause a nice, even heat profile through the room with minimal thermal stratification. Back when we had single glazing there was an extra benefit as the radiator provided a thermal curtain/buffer from cold air falling in from the window and the cool air falling in, mixing with the warm air would divert the buoyant plume and help destratify the room (hence why radiators are typically under windows). Now that we have double glazing the latter doesn't happen and the circulating convection current that the former is supposed to set up never really materialises as most rooms have obstructions that stop the full circulation of warm air and simply cause the warm air to rise to the ceiling and stay there (we've seen 10degC floor to ceiling temperature differences but the typical is around 4/5 degC). The Radfan helps set up that warm air circulation/cyclic convection current by essentially giving the radiator a little top up to get the air moving. It also reduces heat loss through the window by about 35% by diverting the flow of air away from the window a bit. The testing we have done is twofold, field trials with 10 housing associations to see what the behavioral impact is but more importantly we have had controlled and independent testing carried out by the Salford University Energy House (http://www.salford.ac.uk/research/best/research-groups/applied-buildings-and-energy http://www.salford.ac.uk/research/best/research-groups/appli...) that corroborated our own in house testing that showed the Radfan acted as a destratifier (temperature at the ceiling decreased and the temperature at sofa height increased by the same amount), reduced the heat lost through the window, allowed the central heating to turn off sooner (providing a small energy saving that more than offsets the running cost) and most importantly didn't introduce any forced convection on the radiator so the central heating wasn't working harder as there was no extra energy being extracted from the radiator (just a redistribution of the thermal energy already in the room). The data shows that a Radfan will typically decrease the temperature at the ceiling by 1 to 2 degC and increase the temperature at the vertical mid point by a corresponding amount. It varies from home to home and in a very small percentage (less than 0.5%) it has minimal impact, hence we offer the warmer home guarantee so that if a home is in that small 0.5% (which we are unable to define as homes vary so much) then you can return for a full refund - we only want people living with a Radfan if they feel the benefit. This page summarises our independant test results: https://www.radfan.com/pages/energy-saving https://www.radfan.com/pages/energy-saving