How to Insulate an Attic with Fiberglass | This Old House

I'm seeing some open bays around the perimeter and then I'm seeing planks that are nailed down over the joist pace here in the center of the floor we have to pull all these nails and pull up the planks we are not going to pull up all the board's we're going to pull up one or two boards and we're going to blow in loose insulation under the boards and all the open Bay's we're going to use this right here batt insulation all right sounds like a little bit of a cocktail of insulation where you want to get started well I want to get started by cutting these pieces right here they're going to go in the joist Bay into the eaves you give me some measurements I'll do the cutting alright for our first measurement it'll be the length hook the tape on the outside of the outside wall and measure to the inside of this joist is 29 inches next measurement will be the width our joist are 12 inches on center so cut them 10 and 1/2 11 inches and for the width the bat actually comes perforated in four areas which means I can just tear off the last one and it leaves me with 11 inches you see that daylight in there well that's the soffit and that light is coming up through the soffit vent when we install the bat we want to be very careful not to block that opening so you actually pull the bat back a little bit from that opening now we have a nice two inch space here for plenty of air to come up over it here in the eaves we laid our insulation directly on top of the plaster ceiling so we used an insulation with a vapor retarder on it and that's this paper facing exactly now in these Bay's right here there's insulation already in them so I wanted the different insulation one that doesn't have a vapor retarder on it called unphased insulation so why no vapor retarder here because if I use a vapor retarder between the installations the moisture from below can get trapped between the two insulation dampening this insulation here making it less effective now the insulation that we placed in between debate is six inch our 19 insulation we want to get an R 38 so we're going to take a second layer of unphased six-and-a-half insulation lay it on top of the new insulation that we just installed pushing it up tight and perpendicular to the joist we're actually going to cover this floor first then we're going to remove a board and blow the insulation under the floor and why are you doing it in that order well this will keep the dust down when we blow because it's going to want to come up between the gaps and all these boards exactly all right good thinking each bag of this blown in fiberglass insulation covers about 30 square feet when we dense pack it into the floorboards like we're doing I'm going to measure I want to measure about three-quarters of the distance into the bay pull the hose out push it back in now I'm going to turn the blower on and that will blow the insulation into the cavity now as the base starts to fill it dense packs the insulation it will start pushing the insulation back and also pushing the hose out you can actually see the hose coming out on its own so that tells me that the insulation is being packed in there just right so we started off with an r6 what do you think we ended up with we've got over an hour 40 Wow from 6 to 40 this homeowner is going to save a lot of money he sure is going to notice a big difference in right away you

Channel: This Old House

Views: 311,864

Rating: 4.8553128 out of 5

Keywords: This Old House, Ask This Old House, DIY, Home Improvement, DIY Ideas, Renovation, Renovation Ideas, How To Fix, How To Install, How To Build, insulation, Fiberglass, Thermal Insulation, Attic, Do It Yourself, Design, Repair, Interior Design, Construction, Installation Cleaning, Tom Silva, kevin o'connor, tom silva this old house, tom silva house, tom silva construction, tom silva tools, tommy silva

Id: fRVxdWaOJjk

Length: 4min 6sec (246 seconds)

Published: Sun Jan 11 2015