Hello again - it's a long time since I posted anything.
We are having a new room built over the top of our existing single story kitchen - which is a later (possibly Victorian) extension to the main part of the house. The house is not listed, but we think we are being sensitive and also modern, in partnership with our architect. The design has a very large floor-to-ceiling window on the back, South-facing side - maximising passive solar gain and all that sort of thing, with the original thick stone end gable exterior wall of the main house becoming one inside wall, lime rendered and not covered with insulation, the rest of the walls & roof very well insulated etc. I hope you all get the picture.
The FRONT elevation, facing the road was designed to have a one-over-one proper sliding sash window to match the others in the old part of the house, but projecting as an oriel. The big window on the other side, being down to floor level cannot be opening, though it is cantilevered out and has narrow side panes which will have opening upper sections. Buiding control wants the sash window at the front to be replaced with an imitation sash so that the top pane is hinged at the top and the lower pane at the side, to enable it to open wide enough for fire escape. Our architect assures me that the imitation sashes he specifies are indistinguishable from the real thing - unlike the hideous things one sees all around.
We would still like a proper sliding sash if possible. It was going to have to be spring-balanced and thicker to cope with the problems of using wide-gap double glazed panes, but still a proper sash.
Can the experts here (e.g.Biff?) advise about sashes with side-opening bottom panes? I know that they are more common in Scotland - referred to in the Historic Scotland leaflet on maintaining sash windows, but it seems to me that side hinges would only be practicable with traditional cord-balanced panes (though I think there is a local joinery company who do double-glazed sashes with cords and lead weights).
The other issue I'd like to share with the green building experts here is building regs. and insulation. Because of the very large area of glazing, Building control were not happy with the U-value. We and the architect had to decide if we would reduce the glazed area, or if he could negotiate by increasing the insulation. (I was going to ask this Forum's opinion at that stage, but didn't)
The increased insulation won, and was successful in getting approval. The rest of the house is so dark that we were very loath to lose any of the "feature" window, so the (new) external walls will now be two leaves of 100mm concrete block (lime renedered externally) with 100mm Dritherm insulation PLUS 38mm Gyproc urethane laminate on the inside. I was hoping to have all the walls with solid rendered internal surfaces to soak up and retain some of the solar gain from the window, but at least we still have the old house wall to do that - which is always warm anyway because there's an Aga against it down in the kitchen. We are not going for triple-glazing on the big window, though I recognise it would probably be best, because it would be hugely more expensive.
So - any opinions?
Have we made the right decision? The new room will be an interesting mix of traditional and new - gypsum plasterboard (mostly covered with shelves) and also lime render - and I'm afraid the insulation in the roof will be rigid foam, not sheep's wool, hemp or recycled newspaper - and neither is it multifoil!
It's called pragmatic compromise, and saving some money so we can afford a nice oak floor.
We are having a new room built over the top of our existing single story kitchen - which is a later (possibly Victorian) extension to the main part of the house. The house is not listed, but we think we are being sensitive and also modern, in partnership with our architect. The design has a very large floor-to-ceiling window on the back, South-facing side - maximising passive solar gain and all that sort of thing, with the original thick stone end gable exterior wall of the main house becoming one inside wall, lime rendered and not covered with insulation, the rest of the walls & roof very well insulated etc. I hope you all get the picture.
The FRONT elevation, facing the road was designed to have a one-over-one proper sliding sash window to match the others in the old part of the house, but projecting as an oriel. The big window on the other side, being down to floor level cannot be opening, though it is cantilevered out and has narrow side panes which will have opening upper sections. Buiding control wants the sash window at the front to be replaced with an imitation sash so that the top pane is hinged at the top and the lower pane at the side, to enable it to open wide enough for fire escape. Our architect assures me that the imitation sashes he specifies are indistinguishable from the real thing - unlike the hideous things one sees all around.
We would still like a proper sliding sash if possible. It was going to have to be spring-balanced and thicker to cope with the problems of using wide-gap double glazed panes, but still a proper sash.
Can the experts here (e.g.Biff?) advise about sashes with side-opening bottom panes? I know that they are more common in Scotland - referred to in the Historic Scotland leaflet on maintaining sash windows, but it seems to me that side hinges would only be practicable with traditional cord-balanced panes (though I think there is a local joinery company who do double-glazed sashes with cords and lead weights).
The other issue I'd like to share with the green building experts here is building regs. and insulation. Because of the very large area of glazing, Building control were not happy with the U-value. We and the architect had to decide if we would reduce the glazed area, or if he could negotiate by increasing the insulation. (I was going to ask this Forum's opinion at that stage, but didn't)
The increased insulation won, and was successful in getting approval. The rest of the house is so dark that we were very loath to lose any of the "feature" window, so the (new) external walls will now be two leaves of 100mm concrete block (lime renedered externally) with 100mm Dritherm insulation PLUS 38mm Gyproc urethane laminate on the inside. I was hoping to have all the walls with solid rendered internal surfaces to soak up and retain some of the solar gain from the window, but at least we still have the old house wall to do that - which is always warm anyway because there's an Aga against it down in the kitchen. We are not going for triple-glazing on the big window, though I recognise it would probably be best, because it would be hugely more expensive.
So - any opinions?
Have we made the right decision? The new room will be an interesting mix of traditional and new - gypsum plasterboard (mostly covered with shelves) and also lime render - and I'm afraid the insulation in the roof will be rigid foam, not sheep's wool, hemp or recycled newspaper - and neither is it multifoil!
It's called pragmatic compromise, and saving some money so we can afford a nice oak floor.