First period property! (loft insulation advice)

[AndrewB]

Hi guys, Was recommended to stop by here for advice! Nice to be here.

We have just bought an 1888 detached house in Northern Ireland. There are a few projects we would like to take on, but the first (and hopefully easiest?!) is the loft insulation. The house also needs re-rendered at which time I hope to add external wall insulation. Longer term we hope to do a heat pump and solar panels if we can.

Anyway, insulation!

The 'old' part of the house is 1888, solid wall construction with (failing) lime render on the outside. Inside we have a mixture of tongue and groove and (I think) lath and plaster ceilings. When I had a look in the attic I found this note which says that 170mm of fibreglass was added in 2008 to give 270mm total.



However, this doesn't look in great shape. At the far end of the attic is look undisturbed



but closer to the hatch it's a bit of a mess.



I have done a little reading into these properties and understand I need to be careful about moisture control, airflow and all of that. The roof is slate with no felt. I don't believe there to be any membrane or anything beneath the insulation but I realise I did not explicitly check this when up there! Below is a picture of the back of the tiles. It had rained that day, but I am not sure if that is moisture coming in or going out? Also not sure what the white material is on the back of the tiles?



I mentioned that was the 'old' part of the house. There is also a 2019 two-story extension of more modern construction. For some reason there is only 100mm insulation in there, so plan to add 200 more...but...what should I do about the old part of the house?

Any advice much appreciated,
- Andrew

 

[ben81]

Hi Andrew, there are probably people better qualified than me to answer this but I'd get all the fibreglass out due to how much it attracts moisture. We used Rockwool in our Edwardian attic but we also have a breathable membrane under the slates and a PIV in the landing ceiling to keep the air moving into the house. You could insulate with sheepswool but my understanding is eventually even the stuff that has been treated ionically will be eaten by moth. Hemp is another option if you can get it. We chose Rockwool for its apparently breathable properties and fireproofing. Seems to have worked well so far!

 

[AndrewB]

Hi Andrew, there are probably people better qualified than me to answer this but I'd get all the fibreglass out due to how much it attracts moisture. We used Rockwool in our Edwardian attic but we also have a breathable membrane under the slates and a PIV in the landing ceiling to keep the air moving into the house. You could insulate with sheepswool but my understanding is eventually even the stuff that has been treated ionically will be eaten by moth. Hemp is another option if you can get it. We chose Rockwool for its apparently breathable properties and fireproofing. Seems to have worked well so far!

Thanks Ben.

Been reading some other posts and seen the sheep's wool mentioned also. Haven't heard of the hemp though. Are you saying hemp prevents the bug issues?

One other things I realised is that I don't believe there are any vents in the attic... In my old house I had them along the ridge at the top (not sure what it's called) but not in this house.

 

[ben81]

I believe its less likely to be eaten than wool because its cellulose. It was hard to come by when we were doing ours though that's why we went with the rockwool. We initially tried the government insulation scheme but every firm wanted to put in fibreglass so we just bought it direct and did it ourselves. Would you need vents if theres no membrane or felt? I'd imagine the air can move between the gaps between the slates

 

[Lacan07]

Thanks Ben.

Been reading some other posts and seen the sheep's wool mentioned also. Haven't heard of the hemp though. Are you saying hemp prevents the bug issues?

One other things I realised is that I don't believe there are any vents in the attic... In my old house I had them along the ridge at the top (not sure what it's called) but not in this house.

Dont quote me but I believe the bug issue has been sorted, I think it was originally the company now called Thermafleece. There are other manufacturers of sheep wool that have never had any problems. The downside is its quite expensive. Thermofloc is a cheaper alternative, but loose fill.

Many people use Rockwool and there are plenty of debates on the internet as to whether its entirely suitable for old houses. It's supposedly breathable but how does it react to holding moisture or getting wet. I would say your loft with no felt has plenty of ventilation so Rockwool is a candidate in this instance.

 

[Me!]

... get all the fibreglass out due to how much it attracts moisture.

I've never heard that before. Can you point me to any scientific studies or similar please on the subject?

 

[ben81]

I've never heard that before. Can you point me to any scientific studies or similar please on the subject?

Sorry I probably misspoke, i mean it holds moisture/condensation rather than actively attracts it. I forget where I read this but it definitely wont have been in a peer reviewed journal. I understand once its wet its wrecked as well, wheres rockwool or sheep wool can dry out well enough

 

[AndrewB]

Thanks for the advice. Il get some prices for thermafleece and Rockwool and do a little more research into both.

Even if I decide sheep's wool for the old part of the house, might put Rockwool instead of fibreglass over the new part (extension) as they are connected by a common air space. Perhaps over thinking it lol.

How would I know if the existing 2008 fibreglass in the old part was compromised? Tempting to leave it and/or throw it on top of whatever proper product I put down

 

[ben81]

If it feels wet and looks compressed and done in it probably would be best to carefully take it out with all the necessary PPE on, and bag it while you're up there so you leave minimal fibres in the house. I don't think its breathable so would be best out of the old part of the house before adding whatever you decide to replace it with

 

[LadyArowana]

Been reading some other posts and seen the sheep's wool mentioned also. Haven't heard of the hemp though. Are you saying hemp prevents the bug issues?

Clothes/ carpet moths are only interested in ‘animal‘ fibres ( wool, silk, fur, feathers .. ) anything which derives from plants, such as cotton or hemp, isn’t delicious to them. Nothing in the entire universe except a bored Labrador will eat polyester.

 

[AndrewB]

Hey guys, still thinking about what the best thing to do here is. Sheep's wool is very expensive and hemp wool seems hard to get (any advice on getting these products in NI?).

How do I assess if rockwool would be OK for my property?

 

[malcolm]

I would go for rockwool. It's not a problem for breathability. An added advantage is it will pick up signs of failing roof tiles that drip all the time by slumping a bit.

Wants to be neatly applied without gaps to the rafters. 300mm is good. Be very careful not to touch the tiles so less than 300mm might be good at the eaves. Whatever you do it should be a whole lot better than the mess that's been thrown up there in the past.

 

[AndrewB]

Thanks Malcolm. Am I right in saying that "rockwool" is a brand name for a "stone wool" product? Are the different brands I should look for or should I stick to the "rockwool" brand?

 

[AndrewB]

OK, one last question guys!

So I am going to go with the rockwool after plenty of research. I'm panicking a bit about vapor and it condensing in the insulation (first old house).

Trying to decide if I should remove the ~250mm of circa 2008 fibreglass from the old part of my house before doing 300mm rockwool... Or just adding perhaps 100/150mm rockwool over the top?

I'm a bit worried the fibreglass will absorb moisture and compromise beams, but also a good possibility I'm completely over thinking this!

60m2 at 300mm rockwool is quite expensive for this stage of our project but if it needs done it needs done.

Appreciate you guys.

 

[Lacan07]

OK, one last question guys!

So I am going to go with the rockwool after plenty of research. I'm panicking a bit about vapor and it condensing in the insulation (first old house).

Trying to decide if I should remove the ~250mm of circa 2008 fibreglass from the old part of my house before doing 300mm rockwool... Or just adding perhaps 100/150mm rockwool over the top?

I'm a bit worried the fibreglass will absorb moisture and compromise beams, but also a good possibility I'm completely over thinking this!

60m2 at 300mm rockwool is quite expensive for this stage of our project but if it needs done it needs done.

Appreciate you guys.

How has the fibre glass held up so far, does it feel dry, are the surrounding timbers ok? If they not caused any damage so far that should give you some confidence to keep it. Unfortunately this is a decision only you can make.

 

[RoDel]

Hi There, I also have an 1800's house in Antrim and I'm wondering the same thing. What product did you end up going with and how did it do? I had rockwool on my list of things to do!

 

[alexander]

the white stuff on your battens is lime mortar generally used to catch any drips getting under your slate tiles there also seems to be a bit of condensation on the back of the slates, providing you insulate 100mm between the joists & 200mm rolled out the opposite direction to prevent any cold spots it shouldn't matter a great deal what you insulate with as long as you do not block the eaves to allow air flow through out the loft area, from your pictures of the loft area you do have some water ingress getting into the timber which you will not stop without actually installing a membrane under the tiles preferably an air permeable membrane to help prevent condensation build up in the loft.