Roof repair vs upgrade

[JohnMo]

6 hours ago, mjward said:

Aga that has its own dedicated external inlet as per photo

So your only forced ventilation for the whole house is a single bathroom fan. So you really need a fan in the other bathroom and kitchen. The Greenwood ones mentioned can be really from eBay.

 

Adding a humidity activated trickle would ensure the cross ventilation is occurring when and where needed. Example bedroom vents normally closed in the day opening during the night when you are sleep etc.

[scottishjohn]

20 hours ago, mjward said:

 

I don't know too much about it as was fitted by previous owners but I know there is a pipe on the Aga that has its own dedicated external inlet as per photo

 

is this a picture of your roof ?

 cos it looks like you got 2 seperate ones with a valley bewteen them and a dormer as well ?

all these parts need good ventilation 

Edited March 3 by scottishjohn

[scottishjohn]

23 hours ago, mjward said:

But if I go above, I enter the unknown from a planning permission perspective given I'm in a conservation area and from what I read they really don't like roof heights being raised (not to mention the additional work to the ridge boards)

got to be worth a shot --on energy savings grounds at least  not as though you trying to lift roof up more than 150mm? at worst ,probaly less

[mjward]

18 hours ago, Iceverge said:

Say it runs 5 mins on average for 15 times a day at 30l/min. 

 

That's 2250l/day

 

A continuously running dMev fan would at 8l/min would be more like 11520l/day. 

 

That's 5 times the fresh air.

 

Intermittent extractor don't have a good track record of good indoor air quality. 

 

 

 A dehumidifier might be 200w. An order of magnitude greater than a mechanical ventilation fan. EG at least 10 times the running cost. 

 

Also remember whilst it does remove moisture from the air it does nothing for the CO2 and VOCs in the house. 

 

All mechanical ventilation system are the same ultimately . They just suck air out or it push in. MVHR is fancy in that it does both and recovers some heat. 

 

PIV works but it has doubled in price the last few years and it creates cold spots under the vent. That Greenwood fan is about 1/3 of the cost and does the same thing. 

 

The gasses in a house tend to diffuse pretty quickly given half a chance. EG an open door for a few minutes. 

 

You've seen that with the loft. It works in reverse too. You can put your ventilation fan in any room that suits and it'll dry the whole house if run continuously. 

 

 

 

 

 

 

 

Because I've set the overun timer to 60 mins in reality it's probably closer to the dMEv figure. My only concern with it set to continuously running (i.e. lower extraction rate) is it's ability to cope during and after a shower as the reason I changed to that one in the first place was that the previous extractor just couldn't keep up and the bathroom walls looked like someone had sprayed a hose at them.

 

You're right about the dehumidifier cost, its not far off 80p/day (I recently plugged it into one of those power consumption monitors), so would be good to reduce that. My only real concern about adding further ventilation is heat loss. At 4000 sqft and Edwardian construction, it's already costing a fortune to heat and I wonder if the saving of extra ventilation vs dehumidifier would be lost in incremental heating cost?

[mjward]

14 hours ago, JohnMo said:

So your only forced ventilation for the whole house is a single bathroom fan. So you really need a fan in the other bathroom and kitchen. The Greenwood ones mentioned can be really from eBay.

 

Adding a humidity activated trickle would ensure the cross ventilation is occurring when and where needed. Example bedroom vents normally closed in the day opening during the night when you are sleep etc.

There is an ensuite with an extractor, another bathroom with an extractor and a utility room with an extractor. All light switch activated with no overun timer and given the ensuite/other bathroom aren't renovated yet, those extractors are rarely used. 

 

I'm starting to think that the way forward is to change the utility extractor to the one Iceverge recommends and to set it continuosly running and eventually to upgrade the ensuite/other bathroom extractors to either have 60 min overun or be continuously running as well. Hopefully between those 4 that's house ventilation taken care of.

1 hour ago, scottishjohn said:

is this a picture of your roof ?

 cos it looks like you got 2 seperate ones with a valley bewteen them and a dormer as well ?

all these parts need good ventilation 

Yes, basically the roof nearest in that picture is part of a 2010 extension to the 1906 original building. The extension has openings to the original on both the ground and first floor i.e. I view them as one from a ventilation perspective. The extension roof is properly insulated and uninhabited whereas the orginal is the one in question here and has the loft conversion.

54 minutes ago, scottishjohn said:

got to be worth a shot --on energy savings grounds at least  not as though you trying to lift roof up more than 150mm? at worst ,probaly less

Was messing around with some of these U-value calculators and it looks as though I could meet the target values with 75mm insulation between the rafters and 100m on top of the rafters. Throw cross battons then yes I can't see me raising it by more than 150mm and hopefully as you say, their desires seem to be focused on energy saving that this dominates their thought process.

[mjward]

Sorry one last point...

 

Ground floor = utility room extractor  (& AGA)

First Floor = 3x bathroom/ensuite extractors

 

Given it's the loft that is showing the effects of high humidity, will better ventilation in the floors below solve that issue? Or should the loft have it's own extractor?

 

Thanks all for your help so far. Really have a much better idea of what to do now

 

[JohnMo]

1 hour ago, mjward said:

Ground floor = utility room extractor  (& AGA)

You said earlier that the aga had an external air feed? If that is the case it doesn't draw air from the house.

 

So the ground floor only has a utility fan that is light switch activated with no over run timer? And upstairs only one fan that is actually used.

 

If you aren't replacing air and you are developing humidity your house will get damp.

[Iceverge]

Building regs tend to over ventilation but Passivhaus recommends as close as makes no difference 30m³/person per hour. 

 

Do you have 720m³ per person per day? 

 

 

 

 

 

 

 

 

[mjward]

22 hours ago, Iceverge said:

Building regs tend to over ventilation but Passivhaus recommends as close as makes no difference 30m³/person per hour. 

 

Do you have 720m³ per person per day? 

 

 

 

 

 

 

 

 

Sorry I don't have a clue. I've purchased that Greenwood extractor and will replace the utility one with it. I've also changed the Vent Axia bathroom extractor previously mentioned to be on continuously. So it will be both of those on the whole time as the primary mechanical ventilation in the house (in addition to all trickle vents open)

[mjward]

On 03/03/2024 at 11:09, JohnMo said:

You said earlier that the aga had an external air feed? If that is the case it doesn't draw air from the house.

 

So the ground floor only has a utility fan that is light switch activated with no over run timer? And upstairs only one fan that is actually used.

 

If you aren't replacing air and you are developing humidity your house will get damp.

Missed this. Yes that is correct John but pending delivery that utility fan will be upgraded to the Greenwood one recommended and set to continuously run. Additionally I've changed the bathroom to continuously run.

What is good is how much improved the humidity has become since I opened ALL the tricke vents. The first floor was often around 60% RH which is when the dehumidifier was set to kick in but about a month ago I opened all trickle vents and without changing any of the central heating settings, the RH has dropped to around 48% (and that's with my daughter moving down from the loft to move into her first floor bedroom ie with an extra common inhabitant on that floor)

[Hughgo12]

The drimaster type mechanical ventilation type install will help address human comfort and condensation.

 

But from a building fabric point of view it does sound like there's a few things to address which would contribute to living conditions and the ventilating the structure. Without raising the roof, 50mm airgap, 50mm PIR, Insulated PB, eaves ventilation, ridge ventilation, in-line slate ventilators and membrane. 

 

Most of the insulation manufactures will run a condensation risk analysis for you.  

[mjward]

16 hours ago, Hughgo12 said:

The drimaster type mechanical ventilation type install will help address human comfort and condensation.

 

But from a building fabric point of view it does sound like there's a few things to address which would contribute to living conditions and the ventilating the structure. Without raising the roof, 50mm airgap, 50mm PIR, Insulated PB, eaves ventilation, ridge ventilation, in-line slate ventilators and membrane. 

 

Most of the insulation manufactures will run a condensation risk analysis for you.  

Definitely. My preference has been to "correct" issues with the building fabric such as introducing several of the items you list. That said, there is also merit in mechanical ventilation and suspect a combination of the two will be most economical. 

 

On a side note, I've never had Velux loft windows before and after researching replacements (as current frames rotten from years of condensation), I've seen that they have built in trickle vents. Up to the loft I go and lo and behold, they were all closed. Have opened them all and made a note of current humidity and will recheck in a week to see how it's fairing. 

[scottishjohn]

my thoughts are that adding mechanical ventilation is not really getting to the bottom of problem 

when house was built it must have had enough draft through the roof space or it would have rotted away 60 years ago 

 a cols roof must have a good flow or air thorugh it and very well insulated from the living space with no leaks of hot humid air from that into the cold roof area

It really is as simple as that

 you say walls are solid --no gaps ,so there must have been good ventilation from eves when it was built 

 so simple answer maybe to fit a row of slate vetns close to bottom of roof and a higher row near top --unless you absolutl;y sure your ridges are also venting 

Edited March 5 by scottishjohn

[scottishjohn]

On 03/03/2024 at 09:16, mjward said:

At 4000 sqft and Edwardian construction, it's already costing a fortune to heat and I wonder if the saving of extra ventilation vs dehumidifier would be lost in incremental heating cost?

heating is a seperate problem  and if rooms are large enough then easiest way is to build new studs walls inside outer walls with vpaour barrier and insulation in it  

can you afford to loose 140m- 150mm on inside of  all outside walls , would still be very good if you only went for 100mminsulation ,then strapit to leave service void before plaster board ,that way there would be little or no penetrations in the vapour/air tightness barrier 

you then have same spec as a new build !! ,and somehting you can do in bits with not that much upheaval ,good time to rewire if its on the cards 

certainly iwould not otuch original plaster etc --just build inside them

 aslo the itme to retro fit UFH while skirting boards are off -ready for you ASHP at some point 

retro fit UFH can be done in under 50mm thickness 

just suggestions  to bring your house into 21 century  in a an easy doable way for the diy man while still living there 

 

again it is the only sensible way to insulate that sort of house ,

Edited March 5 by scottishjohn

[mjward]

22 hours ago, scottishjohn said:

my thoughts are that adding mechanical ventilation is not really getting to the bottom of problem 

when house was built it must have had enough draft through the roof space or it would have rotted away 60 years ago 

 a cols roof must have a good flow or air thorugh it and very well insulated from the living space with no leaks of hot humid air from that into the cold roof area

It really is as simple as that

 you say walls are solid --no gaps ,so there must have been good ventilation from eves when it was built 

 so simple answer maybe to fit a row of slate vetns close to bottom of roof and a higher row near top --unless you absolutl;y sure your ridges are also venting 

You're 100% correct. Is currently a cold roof and was built on top of a house with lime plaster, open fireplaces and sash windows. It now has modern plaster, closed fireplaces and UPVC windows (albeit with trickle vents) ie a lot of that natural breathability is now gone so I'm thinking slate vents should be introduced. I've not looked at them in detail before and I see for the calculators of how many you need they require you to provide the "required airflow" but it's not clear how to work that bit out

22 hours ago, scottishjohn said:

heating is a seperate problem  and if rooms are large enough then easiest way is to build new studs walls inside outer walls with vpaour barrier and insulation in it  

can you afford to loose 140m- 150mm on inside of  all outside walls , would still be very good if you only went for 100mminsulation ,then strapit to leave service void before plaster board ,that way there would be little or no penetrations in the vapour/air tightness barrier 

you then have same spec as a new build !! ,and somehting you can do in bits with not that much upheaval ,good time to rewire if its on the cards 

certainly iwould not otuch original plaster etc --just build inside them

 aslo the itme to retro fit UFH while skirting boards are off -ready for you ASHP at some point 

retro fit UFH can be done in under 50mm thickness 

just suggestions  to bring your house into 21 century  in a an easy doable way for the diy man while still living there 

 

again it is the only sensible way to insulate that sort of house ,

Unfortunately that was a decision I should have spent more time on 2 years ago when I gutted the house. I've now crossed the Rubicon and rooms are at the final decorating stage so will have to do without but given the rooms have the size to accomodate it, it's certainly something I really ought to have done. Would have made the rewire/replumb a lot easier with stud walls too!

 

Now onto a new(ish) query, as nothing is quite simple... I have what I would describe as "decorative dormers" (there is probably an official term but I don't know it). Essentially decorative protrusions on the roof that I doubt planning permission would let me remove (conservation area & preserving the overall look etc). But I can't work out how they would be treated when it comes to adding insulation over the rafters. Would there be cold spots under these?

 

[scottishjohn]

14 hours ago, mjward said:

You're 100% correct. Is currently a cold roof and was built on top of a house with lime plaster, open fireplaces and sash windows. It now has modern plaster, closed fireplaces and UPVC windows (albeit with trickle vents) ie a lot of that natural breathability is now gone so I'm thinking slate vents should be introduced. I've not looked at them in detail before and I see for the calculators of how many you need they require you to provide the "required airflow" but it's not clear how to work that bit out

Unfortunately that was a decision I should have spent more time on 2 years ago when I gutted the house. I've now crossed the Rubicon and rooms are at the final decorating stage so will have to do without but given the rooms have the size to accomodate it, it's certainly something I really ought to have done. Would have made the rewire/replumb a lot easier with stud walls too!

 

Now onto a new(ish) query, as nothing is quite simple... I have what I would describe as "decorative dormers" (there is probably an official term but I don't know it). Essentially decorative protrusions on the roof that I doubt planning permission would let me remove (conservation area & preserving the overall look etc). But I can't work out how they would be treated when it comes to adding insulation over the rafters. Would there be cold spots under these?

 

what do you see from inside --a flat roof

or can you see the shape -- 

 is that wood work venting the space?

Edited March 6 by scottishjohn

[scottishjohn]

Just now, scottishjohn said:

closed fireplaces

vented at fireplace and capped  or open chimneys?

 

if no vent in fireplace then your chimney will be another source of damp --rain going down them 

[mjward]

8 hours ago, scottishjohn said:

what do you see from inside --a flat roof

or can you see the shape -- 

 is that wood work venting the space?

Yup a flat roof from the inside, hard to see from the pic but basically behind the wood work is just the vertical stone wall extended to the apex of the dormer ie no ventilation

8 hours ago, scottishjohn said:

vented at fireplace and capped  or open chimneys?

 

if no vent in fireplace then your chimney will be another source of damp --rain going down them 

the fireplaces themselves are seal. 3 of the 4 chimneys are capped and when I get this roof work done I will be capping the fourth (just using anti-downdraft cowls, i.e. allow some ventilation but blocks the rain)

[mjward]

So although I've identified the right way forward from an work perspective, I'm struggling on the regulations side.

 

Current loft conversion signed off as such by building control 20 years (by the standards at the time). If I add insulation now, it will require building control sign off again. Will I lose the status of "loft conversion" (ie habitable rooms) because they don't meet the current standards (despite all I'm doing is IMPROVING them with this work)?

 

Unfortunately my local BCO is not being overly helpful on this matter.

[Mr Punter]

1 hour ago, mjward said:

So although I've identified the right way forward from an work perspective, I'm struggling on the regulations side.

 

Current loft conversion signed off as such by building control 20 years (by the standards at the time). If I add insulation now, it will require building control sign off again. Will I lose the status of "loft conversion" (ie habitable rooms) because they don't meet the current standards (despite all I'm doing is IMPROVING them with this work)?

 

Unfortunately my local BCO is not being overly helpful on this matter.

 

No if your loft conversion was signed off it has regs.  If you do other works they will be a separate sign off.