Edward Norton

Sam Benson wrote:That's a purlin, not the top plate?

Did some research. I’m a trained civil engineer but left the profession twenty years ago, so sometimes make mistakes. In the UK it’s a purlin but there appears to be many derivations used in different parts of the English speaking world. I’m sure on-site, construction works will have lots of names for different kinds of purlins / rafters, etc.

Anyhoo, it’s the big beam that supports the rafters near the eves.

My roof has no insulation. It does have a finished floor, staircase and it’s a massive room which I’ll convert to a bedroom and bathroom. It also has lighting and windows, so an easy place to work.

My solution is to use rafter baffles. These are shaped polystyrene that’s principle function is to create an air gap between the underside of the roof and the insulation. Americans use felt tiles on their roofs rather than slate, stone, terracotta tiles in other parts of the world. So a black roof in full sun that’s properly insulated, could get hot enough to melt the felt. The air in the baffle warms up and flows out through a gap at the roofs apex. I have a few issues.

1) The spacing between the rafters is pretty random and generally between 1 1/2 and 3 feet. Baffles are sold in 22 1/2 inch widths and have two channels. I’m guessing new builds have rafters at 2 ft spacing and use 2 x 6’s which means a 22 1/2 inch baffle fits nicely. My options are:
  A) Cut and fit as best I can. My main concern is that they will loose some of their rigidity and might not “bridge” with a sufficient air gap.
  B) Make my own baffles. I would rip down a one inch board into battens and then span the gap with a 4mm thick insulation layer. This would leave a 3/4 inch air gap between battens.
If I was starting from scratch, I’d go for option B but I’ve found a whole stack of unused baffles in the attic, so effectively free.
Option B is expensive but offers more insulation and peace of mind, but might not be code compliant. Thoughts?

2) Near the eves there’s a big purlin, it looks to be 4 by 6 inches.



There’s very small gap between it and the underside of the roof. I think in modern construction there’s an air gap at the eves so the air flowing through the baffles has an entry and an exit. I have no idea of there’s an air gap at the eves. I can’t see any day light but the space under the purlin, towards the eves is pretty small. I couldn’t see anything obvious on the outside of the house either. I’m going to assume there is no gap - possibly why the previous owner didn’t install the baffles but I’ve already expended way too much mental energy on trying to figure out why he did or didn’t do things. My plan is to remove a bit of the corner of the purlin so there’s a 3/4 inch gap between the roof and purlin, to allow air flow into the baffles. Then I’ll box off with a small wall, to great a contiguous air space the full width of the roof behind the purlin. I’m stuck as how to get air from outside into this space. I’ll sleep on it tonight and probably have a solution in the morning, but I thought I’d give you folks a crack at it first, incase there’s something obvious I’m missing. Cheers.

Interesting options L. Do you have trees you can pollard for wood chip? Long term, I plan on planting willow and hazel to pollard and produce chip. I’ve seen people working on a high log bench (like a butchers block) with a machete converting branches into a decent mulch.

Heather Staas wrote:I finally picked up a cheap greenhouse (it's been on my wish list for a few years now ) and fenced in my sideyard, added the space to my backyard.   No more grass.   I'm starting to wonder if my chipdrop pile this summer is going to be ENOUGH instead of wondering how I was going to give away all the extra LOL.  

Looking good - love the herb spiral!

I’ve had four loads so far, which is now in place. I could do with a few more drops for the side garden and front lawn. I’ll hold off until next summer though, as I need to start planting the back first.

Gray Henon wrote:
Sorry, there is no way that product is R15.  Possibly a typo on R1.5.

They sell over a 2 billion sqft a year and it’s ISO9000 company, so no, it’s not a typo.
They also sell in the UK and EU where there are stricter regulations when it comes to makes claims about your product.
This is the same tech that Nasa use.

Pearl Sutton wrote:Edward: Can you use a blower or fan to get the foam out of the wood stuff? That would make it safer to deal with the heavier debris.

That was my 3am thought, except suck, not blow! It went along the lines a trash can, some 3inch hose and my shop vac to build a cyclone and suck them out.

Mike Haasl wrote:

Edward Norton wrote:The walls are badly insulated, so I will repeat what I’ve done in the basement, starting with a thin 4mm R15 layer of insulation

Is that a typo?  That would be some amazing insulation!

Good spot - it’s 5mm thick!

I looked everywhere for something to insulate the basement and provide a vapour barrier. I eventually found some stuff on Amazon:

SmartShield - 5mm 48” x 100’

“ Insulation (R15), Radiant Barrier, Vapor Barrier, Sound Barrier.” - at less than $1 / sqft.

It’s nice to work with and I’ve cut a piece for my car front windshield.

I don’t need all it’s functionality for an attic wall, but I’d use it just for it’s thickness and R value.

Yesterday I headed up to the attic room to get a better hands on understanding. The underside of the roof has no insulation and a mass of roofing nails sticking through the plywood, so now a designated “hard hat” area. The spacing between the rafters is a bit random, so I’m going to have to improvise with the rafter vents / baffles. The rafters are deep enough for 6 inches of insulation. The end walls both have windows which are double glazed. The walls are badly insulated, so I will repeat what I’ve done in the basement, starting with a thin 4mm R15 layer of insulation, then 4 inch studs for regular insulation and then finish with boards.

Under the eves is going to be a long boring job. What I thought was just packing chips is a whole mixture of nasty stuff including bits of old roofing tiles, random off cuts and splinters of wood and ply, and bits and pieces of insulation, including some big pieces but nothing worth recovering. And cat hair . . . On closer inspection I can see evidence of insulation between the rafters, tiny tufts caught on splinters of wood. My theory is that the house once had a fully functioning attic room with an insulated roof. When the previous owner had the roof replaced, everything bar the rafters was removed and a lot of it dumped in the eves, which were then covered up with packing peanuts. So rather than bagging and donating the chips, I now have to sift through, extracting big chunks of ply, the odd board and bag the waste for disposal. Fortunately it’s 4’C outside this morning, so the attic is a comfortable temp to work in as I’m in full PPE.

I knew I could count on some awesome replies - makes me wonder why I didn’t ask earlier!

My blisters are healing but it’ll be a while before I can use that plane. I wasn’t aware I had a problem until I took my gloves off and left skin behind. I was wearing them because I was alternating between axe and saw and plane, mixing stuff up. My soft covid hands are starting to toughen up!

L Johnson’s query gave me just what I was looking for. I hadn’t thought of rotating 90 and using a broad axe. Too many years of gaming have programmed my brain to think “Weapon” not “Tool”. I have a much smaller plane so will have a go with that, following the curves makes a lot of sense. I like the idea of a large spokeshave. I’ve been reading a book on making tools and I think it’s something I could have a go at one day.

Cheers folks, help much appreciated.

On closer inspection, they are about 2/3rds polystyrene and 1/3 cellulose and mixed in together, so there’s no way I’m going to separate them. Bagging and craiglist sounds like the best option.

I should point out that they are rubbish at insulation for those of you thinking of using them that way. They work as a packing material because they create a lot of space which is filled with air. Air can easily move through packing peanuts. So their R value is really, really low. Most insulation works by stopping airflow completely. When I lived in the UK, we had a typical house built of brick with a cavity. The cavity was just air. When we had it filled with a blown in insulation it more than halved our heating bill. A gap was better than no gap, but when air can move its no longer adding much value.

I have 400sqft of eaves, two foot deep. That’s 800 cubic feet. There are 5,520 peanuts per cubic foot, so that’s how I know I have nearly four and half million of them!