Iceverge Posted January 24, 2023 Share Posted January 24, 2023 10 hours ago, MattMiller said: A budget for a knock and rebuild is completely off the table? At the moment the extension is only a en-suit, dressing room, with laundry and cupboard, we don't need it to be glorious, but we do need to improve the icy cold in there. I was actually referring to the entire house but having looked at the sellers photo's I can see that it is in far better condition than I thought. In fact it looks quite finished regarding the interior. Probably worth spending a few bob refurbing rather than pushing the whole lot into a hole with a bulldozer and doing a new build. That's my default answer when it comes to old houses that are in poor condition. 10 hours ago, MattMiller said: . I have a manrose MF150T to go in. enough draw to inflate a hot air balloon. Good, it'll need ducting to the wet rooms however given the layout of the house. If it was a compact shape single point extraction from a central room may have given you 90% of the benefits at 10% of the hassle. Consider a future ESHP location when you're installing the extractor and a silencer as it may be loud. 10 hours ago, MattMiller said: Main bedroom is patio sliding door, its going to go and become a French door, We have the orange shutter door between the bedroom and bathroom and shutters over the bedroom door as well. the glass in the en-suit and dressing room i think is less then half the cold issue, the uninsulated roof is the pain. I would consider holding fire on the windows and doors for now. The roof is top priority. 10 hours ago, MattMiller said: also a mechanical Engineer in oil and gas so yea im confident i can do most things. Excellent, the basics of heat loss calculations will be child's play to you in this case. Well worth getting a handle on the numbers. They often make complex issues very straightforward. 10 hours ago, MattMiller said: The house swallows heat like there is no tomorrow given it's large outside surface area vs internal area. (form factor) 100%, especially the extension. Main house with stone walls actually retains the heat well. They are probably not as awful as the extension with its drastic overglazing. However they are still lightly to be in the region of 1.5-2.0 W/m2K. An order of magnitude worse than a modern acceptable figure. Given their high heat capacity they will resist any sudden changes in temperature, and the interior surface will be close to room temperature leading to good thermal comfort. However they'll still be leaking lots of energy. 10 hours ago, MattMiller said: No mains gas or sewage. we have gas only for the kitchen hobs, and a septic tank. Solar on the roof, intention is to get more and batter storage independent of the main house so as not to affect the feed in tariff I'm guessing oil then. Probably worth thinking about an all electric future at some stage, even if it is 10-20 years away. That means induction hobs (brilliant IMO) and ASHP (great if done well, awful if not). PV is far down the list of priorities unless you have a specifically high summer load than can maximise its use. Get the fabric sorted first. @Marvin's AIM-APE nails it. Airtightness,Insulation,MVHR,- ASHP, PV. 10 hours ago, MattMiller said: That flat roof has to go. Take it down and scrap the lead. Erect a proper pitched roof integrated into the original house. Do you mean to the same height as the main house roof? What would be the benefit of adding this? Yes, flat roofs belong in the Sahara Desert, certainly not in the west of Scotland. Pitched roofs are far more durable, almost never leak, don't suffer from interstitial condensation are cheaper. Easier to insulate and you get space for plenty of insulation and services. 10 hours ago, MattMiller said: . 8% at most currently and we have a velux in the main house roof over the top of the flat roof to give light to a rather dark hall way. we would need to account for this in a full pitched roof. and cost I have no idea what this would be. Max i could rais the roof to the house side would be 100mm. which should give a greater % run off. You'll need to move that velux. The current roof is too close for comfort to the bottom of it as is IMO. 10 hours ago, MattMiller said: Would hard insulation be better, I would rather spend more for something better if we are retaining the flat roof... No, it's success is entirely due to marketing. Apart from a few tricky situations which could have been avoided by better designers there is always a better solution to PIR. 10 hours ago, MattMiller said: Sorry, I'm no building expert, what is a bell cast? It's a shallowing of the roof slope at the eaves. In your case to allow continuous insulation between the loft and the external wall insulation. 12 hours ago, MattMiller said: I assume I use external hard insulation and then roughcast onto that. W cannot insulate the stone part of the house externally as far as I know, it would dry out the stone too much and stop the house breathing. I know I can insulate internally with a fibrous board and lime plaster render though as I helped family do this to their home. External wall insulation (EWI) comes in many forms. Most common is EPS boards. Phenolic boards, rockwool, woodfiber are all used. They normally take an acrylic or silicone render. These are not cheap or foolproof however and some members have had issues. My neighbour used a special roughcast on EPS . Seems to be lasting well. Less common ways to do it are attaching larsen truss timbers to the wall. insulating between, then a vented cavity and rain screen. I have seen pictures online of metal ties being used to hold cement board away from the wall and create a cavity which was then filled with EPS beads. You could always just build another single leaf concrete wall away from the wall and create a cavity. Cheap and very durable but you'd have an extremely thick wall! There's no issue with EWI and stone walls as the insulation moves the dewpoint outboard of the stone. Infact it will help preserve the wall almost indefinitely provided you do a good job keeping the water out too. Sorry about the planning queries, I know little in this area re the UK. Here's a quick drawing I did of a section through your plans to demonstrate what I was thinking re a really good renovation. On the left is before and on the right is after. The lead flat roof is removed and it is pitched to the apex with a substantial overhang and a raised wall plate detail. Similarly the existing pitched roof is given a bellcast and overhang. You can see how the roof insulation ( loft roll is about £10/m2 at 400mm) joins up with the external wall insulation to mitigate any bridging at the wall/roof junction. The EWI runs outside all the existing wall outside the troublesome steel and solid walls. EPS runs at about £35/m2 for 300mm. It is cheap VS the time and render cost so do as much as you can. Take it right down to the foundation and your heat loss thought the uninsulated(??) floors will be minimal and you won't have to disturb the inside of you nice house at all. 1 Link to comment Share on other sites More sharing options...
MattMiller Posted January 26, 2023 Author Share Posted January 26, 2023 Thank you for this, it make it so much more bearable to understand than online google solution finding. 10 hours ago, Iceverge said: I'm guessing oil then. Probably worth thinking about an all electric future at some stage, even if it is 10-20 years away. SOO, the house is a Biomass boiler, Put in by the previous owners. Futureproofing would mean air sourced or ground sourced heat pump (we have enough land for this so is a potential), however the floors are concrete so also means pulling up the whole house unless we want mediocre radiator solution... There is electric floor heating in the En-Suite and shower room and kitchen, No idea why they did not go for hydronic, En-suite is a consideration for this as we would like to replace it at some point, the rest of the rooms I think will have to remain, and get very little use because of the cost to run them. Radiators are plumbed with heat going in at the top and out at the bottom (on the same side of the radiator) and TRVs placed on the out flow, and in the same room, on another radiator on the inflow.... I mean come on! Even flexable braided hoses were used to plumb in one radiator which inevitably blocked as there would appear to be no inhibiter in the system. So the house is in great condition (appart from minor issues), and just a half assed job on the extension by the owners 2 owners ago. (Ironically I know where they live , They also stole from the queen by removing a old telephone box from our grounds! ha ha. There are quite a few rubbish finishes around the place that lets the house down but they are only finishes so can be repaired over time) Regarding your images above, the new proposed roofline to the right, is this essentially a flat roof from the Apex of the main house roof or would a new apex roof meeting perpendicular be another option? How do I account for the step in the glazed wall? on your design or Perpendicular design (other than get planning to remove the step and make is square). Removing the velux is not an issue, we could essentially put this in again or another lighting source such as a fixed roof window. Link to comment Share on other sites More sharing options...
Radian Posted January 26, 2023 Share Posted January 26, 2023 (edited) You have to consider the best solution for the most important issue which is the roof of the extension. It needs at least 200mm of rigid or 400mm of fibre insulation and to make it 100% effective it needs to be continuous on the outside of the structure. To do this with a flat roof means adding 200mm to the top of the existing roof. Insulation between rafters won't cut it as you'll be recreating a cold roof with all the ventilation and efficiency problems. For this reason you need to consider an apex roof which will provide enough room for you to build it up as a warm roof (or decently insulated cold roof). You can de-construct the sloping section of the original roof over the bedroom and carry the slope along to cover the extension. You could 'fly' the roof over the cutaway corner to make a little covered area (corner post or cantilevered) if you don't want to extend out into the corner. You can do a cross hip roof (adapt this example picture to suit) Edited January 26, 2023 by Radian 1 Link to comment Share on other sites More sharing options...
Iceverge Posted January 26, 2023 Share Posted January 26, 2023 Can you post accurate external dimensions of the house and I'll throw together a sketch if I get a chance Link to comment Share on other sites More sharing options...
MattMiller Posted January 26, 2023 Author Share Posted January 26, 2023 7 hours ago, Iceverge said: Can you post accurate external dimensions of the house and I'll throw together a sketch if I get a chance So these are the wall dimensions, there is a 250 overhang of the roof on all sides apart from the side with the green arrow, it is only about 100mm Where the red arrow is there is a step out for the main bedroom wall approx. 100mm , but I thought that i could use this space for external insulation and render. taking it out to the main body of the house. the height of the roof along the bedroom wall is lower than that of the flat roof as there is a slope in that see attached photo. this difference is about 680mm. the gable end of the main house (bedroom wall) has a triangular sloped roof, sorry I don't know the correct name for this. I know this is vague, but to do an apex roof, what would you expect the cost to be? Any idea on what planning would be required? or would it just be a building warrant. Remember we are in Scotland. Anyone wanting to come give me a hand , free bed and board and i might even open a special whisky for you! Link to comment Share on other sites More sharing options...
Radian Posted January 26, 2023 Share Posted January 26, 2023 Looking at the agent's photos you linked to, the language of your property permits the use of shallow pitched roofs: This may help inform a suitable design. Harmonising the hipped edge section over the bedroom with its lower soffit level is one of the main challenges. By the looks of it though, the soffit line might just continue along forming a slight brow over the glazing (which is set back a little way). The pitch of this roof section would have to drop sufficiently to span the extension which is getting on for 9m! I estimate the pitch would have to be 33o on these three new planes: 1 Link to comment Share on other sites More sharing options...
Radian Posted January 26, 2023 Share Posted January 26, 2023 Only had M$ paint to hand 😂 but, Link to comment Share on other sites More sharing options...
MattMiller Posted January 28, 2023 Author Share Posted January 28, 2023 @Radian thats great, i actually had to double take and spot the difference there. it would be far more fitting with the house I agree. On 26/01/2023 at 22:46, Radian said: Only had M$ paint to hand 😂 but, only issue i see is without changing the pitch angle of the roof over the bedroom we would have to alter the bedroom roof as well on the main house. great idea though. We could of course have a different pitch on the back of the house to that on the gable end of the house. not sure how that would work. what do you mean regarding the wording of the house and shallow pitched roof. Link to comment Share on other sites More sharing options...
Radian Posted January 28, 2023 Share Posted January 28, 2023 21 minutes ago, MattMiller said: We could of course have a different pitch on the back of the house to that on the gable end of the house. not sure how that would work. what do you mean regarding the wording of the house and shallow pitched roof. In the big scheme of things, re-doing the hip edge slope might be a relatively small modification - depending on the method of construction originally used - but would be far more aesthetically pleasing. Next time you're up in the loft, snap some photos of that end. Roof work on occupied houses is a bit scary but you can sequence the works to minimise exposure and time it with good weather forecasting. What I meant by 'language' was just my flowery way of referring to the variety of different shallow slopes already used for your roofs. By way of contrast my own house has a number of pitched roof components and they're all set to the same strict 49o angle - even a small dormer and lean-to bay. I would call this a strict language vs. a loose language. In other words you have licence to set an arbitrary pitch to achieve a specific ridge height (the current one for the main house) over an arbitrary span. Link to comment Share on other sites More sharing options...
MattMiller Posted January 31, 2023 Author Share Posted January 31, 2023 On 28/01/2023 at 21:56, Radian said: In the big scheme of things, re-doing the hip edge slope might be a relatively small modification - depending on the method of construction originally used - but would be far more aesthetically pleasing. Next time you're up in the loft, snap some photos of that end. Roof work on occupied houses is a bit scary but you can sequence the works to minimise exposure and time it with good weather forecasting. What I meant by 'language' was just my flowery way of referring to the variety of different shallow slopes already used for your roofs. By way of contrast my own house has a number of pitched roof components and they're all set to the same strict 49o angle - even a small dormer and lean-to bay. I would call this a strict language vs. a loose language. In other words you have licence to set an arbitrary pitch to achieve a specific ridge height (the current one for the main house) over an arbitrary span. So the main bedroom has an open roof space into the eves of the roof, meaning changing the hip slope would have to change the inside of the house as well... I know the overall look would be far better but I feel with a 4 month old its going to be too much of a change and unfortunately cost at this stage. (pending lottery results tonight I guess.. ) If I could do the work myself it would be great, but I think we are quickly getting into more than a one man job. @Radian any idea on what is required to make this type of change. planning, structural engineer sign off etc? Will get photos.. Link to comment Share on other sites More sharing options...
Radian Posted January 31, 2023 Share Posted January 31, 2023 1 hour ago, MattMiller said: If I could do the work myself it would be great, but I think we are quickly getting into more than a one man job. Obviously that's your call. Seeing as how you're not so confident perhaps you should bring in a builder and discuss the idea. It always looks simpler from afar, but it's quite a modest alteration IMO. If you plan to live here for the long term you need to sort this nightmare extension out and do it in a way that gives the charm back to the house (it's still quite charming from most angles!). Link to comment Share on other sites More sharing options...
Iceverge Posted February 1, 2023 Share Posted February 1, 2023 Plus one for that. It is a lovely house otherwise. Over the 40 plus years you may spend there it'll be well worth it. Get it as good as you can now. Link to comment Share on other sites More sharing options...
MattMiller Posted March 10, 2023 Author Share Posted March 10, 2023 @Radian thanks for the nice remarks on the house, dream home and went all in on securing this one, that said the alteration costs are out of budget for now. Planning going forward is to redo the flat roof as best as possible and a builder to quote and design as mentioned before. With the quantity of lead on the roof, the scrap value is impressive enough to get new osb, insulation and rubber roof to tide us over until the main redesign can happen. Currently leaking like a sieve. What I could Do with is help on the best insulation solution for this meantime. Currently a cold roof with no insulation. Option 1 Warm roof, replace existing osb3 18mm, damproof membrane, 50mm PIR, 12mm osb3 and rubber, raises the roof 65mm out of availible 75mm. Cant raid much more due to the Velux in the roof and the slate line. Could put in rock wool below the roof im the void .. Option 2 100mm insulation between rafters leaving 50mm air below new 18mm osb3, further 50mm insulation board below the rafters, and ecowool on the plasterboard roof and damp roof membrane Option 3 Rubber, 12mm osb3,50mm insulation, damproof membrane, 18mm osb3, airgap to eaves as in a cold roof, 100mm insulation, earthwool plasterboard (thought was that the extra insulation on the warm roof side might prevent the cold air penitration on the 70sqm flat roof, if only a little) Any thought or problems you see here for any option. New pitched roof may have to wait a few years, but the cost of the lead as scrap should cover the majority of the supplied meantime. Any pointers where I might be going wrong or could improve meantime. We have had 3 quotes from builders so far. Link to comment Share on other sites More sharing options...
Iceverge Posted March 12, 2023 Share Posted March 12, 2023 The safest method is the pure warm roof, with all the insulation above the Rafters. A hybrid option can be done with between and over. Roughly 50mm of PIR at 0.022w/m2K over the top and 50mm of batt insulation below the OSB would be ok. Play with Ubakus.com for ideas. Any more and you'll risk pushing the dew point too far outboard. This will mean that water vapour will condense in the roof and you're back in the same place. Making it a cold roof with insulation only below/between the rafters would work but I would want a bulletproof vapour membrane below the insulation and some really clear ventilation above it. This may eat too much into your head height. As a curved ball could you opt for pre insulated metal sheeting as it's not a long term solution. https://www.steelroofsheets.co.uk/products/kingspan-ks1000lp-lo-pitch-roof-panel/ 80mm panel foam jointed and max 80mm rockwool batt insulation below should be about a U value of 0.2W/m2K and small labour costs. Link to comment Share on other sites More sharing options...
MattMiller Posted March 12, 2023 Author Share Posted March 12, 2023 @Iceverge thank you for this. Will look at those sites. When you say combination of warm and between the beams. Do you mean with an airgap below the osb or direct onto osb when you have a thin warm roof? How do you know how much is too much to avoid a dampness with the dew point. Are there calculations for this or experiences you can relate to? Thanks fella Link to comment Share on other sites More sharing options...
Iceverge Posted March 12, 2023 Share Posted March 12, 2023 10 minutes ago, MattMiller said: When you say combination of warm and between the beams. Do you mean with an airgap below the osb or direct onto Mineral wool batts pushed up against the OSB. https://www.ubakus.de/en/r-value-calculator/index.php?is the one I play with. 11 minutes ago, MattMiller said: How do you know how much is too much to avoid a dampness with the dew point. Are there calculations for this or experiences you can relate to? Have a look at that calculator, you may need to create an account but it's free and it'll give you a good feel for it. In principle if you had a 100% solid vapour barrier you could have all the insulation below the roof structure. The issue here however is that the roof will never be warm enough to dry if any vapour gets in there. That's why there's so many issues with hybrid and cold roof designs and people are much more comfortable with a fully warm roof. Link to comment Share on other sites More sharing options...
MattMiller Posted March 12, 2023 Author Share Posted March 12, 2023 7 minutes ago, Iceverge said: Mineral wool batts pushed up against the OSB. https://www.ubakus.de/en/r-value-calculator/index.php?is the one I play with. Have a look at that calculator, you may need to create an account but it's free and it'll give you a good feel for it. In principle if you had a 100% solid vapour barrier you could have all the insulation below the roof structure. The issue here however is that the roof will never be warm enough to dry if any vapour gets in there. That's why there's so many issues with hybrid and cold roof designs and people are much more comfortable with a fully warm roof. Ok so I have had a look at this and I'm not 100% what I'm reading. What I have tried to put in from unknown plasterboard there is about 200mm air before the structural timbers and osb on top. Max osb I could build a warm roof with would be 50mm as the build would be Plasterboard , structural rafters ,18mm osb, membrane, 50mm PIR boars insulation, 12mm osb3 and then rubber. Giving me about 10mm clearance from the tiles on the main roof. In theory I could reduce tge slope of the last tiles so as to Rais the bottom edge or would cutting them be an option? Would rather not.... If I some how raised them then I could get 100mm insulation in there.... Link to comment Share on other sites More sharing options...
Iceverge Posted March 12, 2023 Share Posted March 12, 2023 How about that if you can make it out. With a warm roof and such a thin layer for insulation you'll be at poor U value. That's why I think a metal panel might be better. Link to comment Share on other sites More sharing options...
MattMiller Posted March 12, 2023 Author Share Posted March 12, 2023 I think I'm understanding now. Thank you. No matter what we do here with such a small insulation is going to be poor. Absolute out the box thinking here. If I place the osb to the underside of the structural beams... damp membrane over and in-between completely sealed off. insulate between rafter and 50mm on top. 18mm ply and Firestone rubber. Leave the gap below the rafter essentialy not Insulated but make a sandwich of insulation in the roof as such... Whats the thoughts here. Stupid idea? Link to comment Share on other sites More sharing options...
MattMiller Posted March 12, 2023 Author Share Posted March 12, 2023 Link to comment Share on other sites More sharing options...
Iceverge Posted March 13, 2023 Share Posted March 13, 2023 With insulation in between the rafters the dew point will be much nearer the inside of the house in cold weather, the roof timbers will get damp and especially when they are almost completely surrounded by impermeable PIR they will stay wet. The DPM is really a mute point in the case above as the moisture comes from the house. How to build a moisture-safe flat roof | SIGA Have a scan of their hybird/compact roof here. It may give you options. I wouldn't do it without ensuring the workmanship was very good. The internal variable membrane needs to be done really well. Link to comment Share on other sites More sharing options...
MattMiller Posted March 13, 2023 Author Share Posted March 13, 2023 @Iceverge thanks for the link. Interesting comment on the page “In a compact roof assembly featuring Majrex®200, and using a high quality rigid insulation with a lambda value of < 0.026 W/mK, you may only need as little as 60 mm of insulation above the roof deck to ensure a safe construction. We see this as a safe solution, and are happy to write a warranty for our product, and to perform condensation risk calculations for our customers.” In essence this is what I've been looking for. I have contacted a building contractor to get them out for costing a pitch roof. Slowly seeing the benifit. Would like to know how the condensation calculations work. Ie first principles. Such a difficult place to be as we have a leaking roof. Want to do the best job, but stuffed for the cost of repair. Does annoy me when people cover up mistakes like this as I just couldn't bring myself to sell a house with this problem. Link to comment Share on other sites More sharing options...
ADLIan Posted March 13, 2023 Share Posted March 13, 2023 I greatly doubt that you would get a UK based insulation manufacturer or waterproofing system manufacturer to promote a hybrid flat roof, not without many caveats! They are specifically warned against in BS 5250 and BS 6229. The Scot Regs push true warm roof detail (and avoid cold deck). Link to comment Share on other sites More sharing options...
Iceverge Posted March 13, 2023 Share Posted March 13, 2023 I suppose there is situation where you could just put the Siga majrex /Intello plus etc membrane inside your current ceiling, ensure the RH in the house is low, let the roof slowly dry to the inside then pump something moisture resistant and permeable like EPS beads behind the membrane. I think it theoretically should work, again if you again have a totally sealed membrane, but I very much doubt anyone is going to offer you a warranty. I know funds are tight but is there any possibility of borrowing the money to do the job properly now? Even with interest payments it'll be cheaper than doing the job twice. I can't imagine a bank not being receptive to fixing a leaking roof as it's sheltering their money as much as yours if you're mortgaged. Link to comment Share on other sites More sharing options...
MattMiller Posted March 13, 2023 Author Share Posted March 13, 2023 7 hours ago, ADLIan said: I greatly doubt that you would get a UK based insulation manufacturer or waterproofing system manufacturer to promote a hybrid flat roof, not without many caveats! They are specifically warned against in BS 5250 and BS 6229. The Scot Regs push true warm roof detail (and avoid cold deck). Can you point me to the Scottish regs on this. I'm actually wondering if I can lower the roof when I take the osb off to accommodate for more insulation and warm roof setup. This is busting my head. That and I'm struggling to did a builder to come see if a pitched roof is doable. Link to comment Share on other sites More sharing options...
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