calumm

I'm looking to get new dMEV extractor fans (i.e. with continuous trickle ventilation) in our kitchen and two bathrooms, and to get trickle vents installed in the existing windows in the other rooms (most do not already have them). Off the hall, we have 2 bedrooms and a bathroom at one end; and 2 bedrooms (including ensuite), a sitting room and a kitchen at the other end. We have an ensuite bathroom off one of the bedrooms. We have a family room (an extension, leading to the garden) off the kitchen. The kitchen is effectively internal, with no windows. The kitchen and family room are connected via a 1.3 m wide entrance to the family room, and also the space where the old kitchen window was; so they are more-or-less open plan. The house is around 1930, so it is probably quite leaky air-wise. I have a few questions, mainly about the resultant air circulation in the house. Q1 If we put a trickle vent in the ensuite bedroom, will most/all of the air going out of the ensuite bathroom fan be replaced by air from the trickle vent in the ensuite bedroom? And therefore won't generate much circulation from the rest of the house? Similarly, our family room already has 6 trickle vents. So most/will all of the air going out of the kitchen fan be replaced by air from the trickle vents in the family room, not generating much circulation from the rest of the house? This might leave the other bathroom fan to provide the suction for the three other bedrooms and the sitting room. Also, as two bedrooms doors are beside the bathroom door, and the other bedroom and sitting room are at the other end of the hall, might the latter (other bedroom and sitting room) struggle to get circulation? Q2 Our sitting room has a bay window with three windows. Should we get a single trickle vent, or trickle vents in all three? Similarly, the ensuite bedroom has a main window and a further smaller window - should we get trickle vents in both? Q3 Should we get trickle vents in the bathrooms (i.e. where we are installing the fans)? Q4 Our door are generally quite old and ill-fitting (e.g. they don't full close, or are slightly askew). There is typically 0.5 to 1 cm gap at the bottom. Should this be sufficient? Thanks - Calum

[Reposting in correct forum] I need to replace the old fan in my bathroom, and I'm trying to decide between dMEV (trickle, with humidistat) and single room heat recovery. My house (ground floor flat) is around 1930, with un-insulated cavities (currently looking at insulating them, and also improving ventilation). The main benefit of SRHRV is the heat recovery aspect. Additionally, the air coming in can be filtered. However, I'm also trying to work out what the possible disadvantages of SRHRV could be, so that I can make a more informed decision. Here's what I've come up with so far: More expensive to purchase. dMEV would help to ventilate the rest of the house, by pulling in fresh air through trickle vents etc. With SRHRV, would this be reduced, as air is being replaced directly in the bathroom; and would there therefore be less ventilation for the rest of the house? Air coming into the bathroom, while partly heated, would still be cooler than the air already there, so this could make it cooler after a shower (some reports online mention this). Clearing of moist air would be slower, as the fan is only extracting for 50% of the time (at least, for single-fan units which switch every 70 seconds or so). (Again, mentioned online.) Might clearing of moist air also be slower because some of the air in the vicinity of the fan would be fresh air which had only just been brought in? These are my speculations as to the downsides of SRHRV. Do they seem valid? Is there anything else? Thanks - Calum

Yes, I would have meant dMEV. I'm looking at the single fan, reversing SRHRV units. Thinking about installing fans in kitchen and bathrooms, and only going to PIV if we still need it. Also, I posted in the wrong forum - reposted in Ventilation.

I need to replace the old fan in my bathroom, and I'm trying to decide between MEV (trickle, with humidistat) and single room heat recovery. My house (ground floor flat) is around 1930, with un-insulated cavities (currently looking at insulating them, and also improving ventilation). The main benefit of SRHRV is the heat recovery aspect. Additionally, the air coming in can be filtered. However, I'm also trying to work out what the possible disadvantages of SRHRV could be, so that I can make a more informed decision. Here's what I've come up with so far: More expensive to purchase. MEV would help to ventilate the rest of the house, by pulling in fresh air through trickle vents etc. With SRHRV, would this be reduced, as air is being replaced directly in the bathroom; and would there therefore be less ventilation for the rest of the house? Air coming into the bathroom, while partly heated, would still be cooler than the air already there, so this could make it cooler after a shower (some reports online mention this). Clearing of moist air would be slower, as the fan is only extracting for 50% of the time (at least, for single-fan units which switch every 70 seconds or so). (Again, mentioned online.) Might clearing of moist air also be slower because some of the air in the vicinity of the fan would be fresh air which had only just been brought in? These are my speculations as to the downsides of SRHRV. Do they seem valid? Is there anything else? Thanks - Calum