The life of two scientists, creating a small home, in big mountains

Retrofitting Rafter Vents – A Hardcore DIY to End 2017

During my rental years, I was obsessed with buying a house. I was not only looking forward to owning my own place, but also to renovating and creating in it. It sounds crazy because renovation is basically spending money to create work for oneself, but it makes sense if you like tangible tasks and working with your hands. I have to admit, although I knew I’d like renovating, I did not know I’d like it this much. I almost do not mind doing it for living, which is the most one can say before actually doing it for living.


The real test for my love and commitment came a couple weeks prior, after we decided to beef up our attic insulation. It is necessary to say the least, since we have only R19 in our attic in a zone calling for R49 to R60. We also like the idea to make our house run more efficiently, even through the cost of adding insulation takes years to pay off. But it is incredibly challenging to add insulation into our attic, due to the roof trusses system and the 4:12 pitched roof.


Why? Here is the logic – by the way, please do not tell me if I am wrong, because we are already waaay too far into the process and there are 1100 pounds of cellulose insulation currently sitting in our garage. Ha!

Basically, because of the trusses, we have to use blown-in insulation instead of laying down fiberglass batts. And due to the soffit venting system, we need to retrofit rafter vents to ensure adequate air circulation in the attic. If you do not know what rafter vent is, here is a video. It is basically a piece of foam or PVC board that has build-in tunnels, and it is meant to be installed tightly against the top plate of your exterior wall pointing up, so fresh air from the soffit vent can rise along the cold roof, out from the roof ridge vents, and bring moisture out with it. Without rafter vents, loose insulation can block the soffit vents and moisture will be trapped in the attic and cause rot.  

Typically, rafter vents are installed before the ceiling drywall is hung, allowing workers to stand below the roof structure and easily staple the rafter vents onto the plywood subroof. But in our case, we had to retrofit them in, which means crawling into the tight corner where the roof rafters meet the exterior wall, and stapling the the rafter vents to its position.


When I say tight, I mean tiiiight. A regular size guy will not be able to reach the top plate unless he is super flat and has ridiculous long arms. It happens to be that Slav is a regular size guy with regular size arms, which makes me the chosen one to crawl into corner and staple the vents.


As any good husband would do, Slav raked away the loose fiberglass insulation to give me a few feet of clear working space. It was nice for him to do that because moving around 55-year-old fiberglass is incredibly dusty (our camera would not even focus). But he did it so I did not have to crawl through loose fiberglass and plant my face into it, so #husbandoftheyear. And as a good wife and a hardcore DIYer, I crawled into the corner, carrying one rafter vent at a time, and stapled it onto the top plate.


See the nails protruding out of the plywood subroof? I had to keep my head down to prevent them from protruding my dura. At least they are 3-month-old nails, so they do not have rust on them yet.

One down, 33 more to go.



After each rafter vent was stapled down, Slav piled the old insulation against the corner as high as he could without blocking the vents. It makes blowing cellulose easier, but more importantly, piling the fiberglass insulation against the corner allows us to have better insulation in majority of the attic. Here are some nerdy schematics for my argument:

Figure 1. The allowance. We can only add loose insulation up to the top of the rafter vents, which is 16″ from the attic floor. And trust me, we tried to buy rafter vents that are longer than 52″ and really did not find any affordable options. That is because that with modern roof pitch (steeper) and better insulation materials, 52″ on the roof usually gives plenty of rise (height) for effective insulation. But we are dealing with really lower roof pitch, so 52″ on the roof only gives us 16″ rise.

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Figure 2. The normal insulation strategy. We already have 8″ fiberglass insulation in the attic, which gives us R19 (R 2.375 per inch).  Adding 8″ cellulose gives us another R30 (R3.7 per inch), brings our attic insulation to the minimal requirement in our zone, R49.


Figure 3. The improved insulation strategy. Packing fiberglass insulation along the exterior perimeters resulted in 5″ fiberglass insulation in most of the attic, which gives us R12. Thinner fiberglass means that we can now add deeper cellulose on top, 13″ to be exact, which brings total insulation value to R60! Of course we would need more cellulose for this to work, that is why we ordered a whole pallet of this stuff.


Interestingly, by ordering more insulation, we actually saved 37%! Here is the breakdown: we got a pallet (36 x 30-pound bags) in order to achieve R60, and we paid $450 (free shipping since we bought from Home Depot website) before tax. If we had bought less, we would have to order the retail type, which are 19-pound single bags at $14.25 per bag, and we would need 50 bags of them to get to R49. This would have costed us over $710 before tax! So paying 37% less for more and better insulation? Deal!


While moving insulation around, we also taped the gaps on ventilation pipes and closed the attic-to-soffit opening with heavy plastic. This plastic functions as a temporary support for the insulation above, allowing us to open the soffit and dry wall it from below.



Let me tell you, retrofitting rafter vents is safely to say the four circle of hell. Maybe because we are too greedy… for more efficiency? I do not know. But four hours later, we crawled out of the attic looking like this:



Anyone knows how to get fiberglass out of jeans?


Just to make the information complete, there are baffles designed for retrofitting you can buy, and it is plausible to cut open from the outside and feed the baffles from the outside (here,  here, and here). We did not want to disturb the newly installed gutter and create more work for ourselves, and all the retrofitting vents are a bit shorter to our need.

So here we are, crossing off most of the things on our insulation to-do list. The last thing we need to do before the blow is to lay down Ethernet cables, which Slav will tackle himself this week:

1. Order the insulation material
2. Seal air gaps, realign and tape-secure the kitchen vent
3. Scoop the insulation out of the kitchen soffit and close it from the top
4. Even out the existing insulation
5. Lay down Ethernet cables for future use
6. Install rafter vents
7. Prepare the garage wall for blown-in
8. Book the machine and it will be the Blow day!

We are so pumped to blow!



What’s in Store for the Ranch House in 2018


The B.L.O.W


  1. Fred Eaker

    Thank you so much for sharing photos and describing your process for adding attic baffles. I have the same task ahead of me in our late-70s ranch in NC. I have been scouring the net for real-world examples. I have some extra rigid foam board that I may use up before purchasing the baffles as you have. Thanks again! Great blog!

    • Alison

      You are very welcome! It is quite a task but it does give us peace of mind. Good luck, and feel free to send me any questions you might have. Have a good holiday week!

    • Matt

      This looks exactly like my attic. Really nice to see how you did it. Did you Install these on every rafter? If so, how many were there? I did a rough count and it was something like 170 😬

      • Alison

        Hi Matt! Yes we installed in every rafter. Only used 44 because our house is small. Combined with the roof ridge vent it works well. It is a messy product. Wear a 3M and stay safe!

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