Our interior insulation will be mineral wool r23, then 1/2 plywood sheathing. Here is where the debut comes in. I would like to put 3/4 rigid board insulation on the outside to help with thermal bridging and to help as an air barrier. Questions on house wrap.
About ten years ago, give or take, Green Building really took off and became the focus on home building. The magazines all had the latest, greatest, bestest methods to get the most energy efficient home possible. Then the following month, they had a new, different way to achieve this. The vast majority of these new methods where based on insulating the walls. What I struggled with when reading everything that they where doing was the R rating of the windows. Why spend tens of thousands of dollars more on your walls to get an R value into the 20's when you have a window on every wall that is R3?
Since heat rises and cold settles, the biggest thing is what's happening in the attic. R60 is about as good as you can get and it's super cheap and easy to do with blown in insulation. Just keep putting it in there until it's two feet thick and NEVER go into your attic again. So that leaves the walls. How to improve the walls. Used to be that you just went thicker using 2x6's to get R19 over 2x4's at R13. The problem with walls is the wind. If air can get through the siding, and then the sheething, it defeats the insulation regardless of how thick it is. House wrap does a lot to solve this and it should have been named "wind barrier" not water barrier since that's kind of misleading. It helps keep water out, but that's not too hard to do and not why it's important. Keeping the wind out is why you need house wrap. There are different grades of house wrap and Hardie makes one of the best in my opinion. The goal is to seal it off so air does not get through it.
As with anything, there are experts that will tell you that you need to go to their extreme version to do it right. In order to do this, you will spend a fortune achieving this level of perfection. For some, it's makes them feel better to have done all this, but in the end, the cost savings are not there. I prefer to follow best common practices and shy away from the latest, greatest idea of the day. Spend a fortune on your walls, and you still have R3 windows. Get triple pane windows and you increase your R value a little bit, but it's not worth the cost. There is even 4 pane windows out there that are awesome if you live next to SFO Airport and you need to stop the noise, which I know a person who did this with good results, but the cost of those windows was freakishly expensive!!! Look at how 99 percent of all houses in your area are built and you will find that nobody is spending the extra money to create super efficient walls. The reason is that it's not cost effective to do so. And for those willing to spend the money, then spraying closed cell foam is the best thing out there.
I prefer OSB over plywood. For less money, you get a better product. Half inch construction grade plywood is full of voids and in every sheet, you will have area that blow away on the back side when nailed. I do not believe there is such a thing as half inch construction grade plywood that doesn't have areas of it that you only have two layers of wood. While most of the sheet might be fine, it's never going to be all of it. I rarely use house wrap anymore since Zip Siding has become available. That is my favorite by a huge margin!!
Here, vinyl isn't a premium product. It's used to hide wood issues on older homes and a red flag when looking to buy a house. Hardie is very popular.
, not that I have to be particularly airtight. (44th parallel, so many more 'heating days' than 'cooling days'.) I have air equalization in mech room for Nat Gas furnace and WH, so drafty windows aren't often obvious. Two 'small' and attached garage on upwind side 5 'various' and an entry door alee.