We've used a few different approaches to insulation in this house. The common denominator being spray foam insulation. This insulation type is an expanding insulation that seals gaps, cracks and joints within the cavity it's filling, hardens into a strong shell and acts as its own vapor barrier. It carries a true R Value of R6 per inch and so we're able to achieve a wall system of R28 (closer to R30 if we count sheathing and air films, etc) in our walls. The walls will actually perform at that level too - unlike many fiberglass insulation installs that perform well below their label of R19. In order to combat the effect of potential thermal bridging through the studs -we used the dri-side clip system and air space behind our siding (R2). Another way to do this would be to install rigid insulation sheathing (or to have used structural insulated panels) but our builder wasn't comfortable with that approach - given that the hardie plank siding is heavy and he worried about screw length and weight and the ravages of time.
In the new walls (and accessible existing walls), we used a closed cell spray foam insulation at all wall cavities and rim joists (read more about the differing types of insulation down below) and in the existing walls we cored from the exterior, filled the cavities with dense pack cellulose and used a bio-based expanding foam to plug the holes.
A view of the insulation in the walls and roof deck. Note the yellow post it note I've left the insulators where I think the fill is a bit too shallow. Just like proofreading a document, you need to walk back through an installation after it's complete to make sure everything is filled just so because the foam expands during installation and takes a bit of time to cure.
On the roof decks and ceiling - we had originally planned to use 8" of spray foam at the bottom of the roof deck to get an R50+ rating (the higher the R value the better). However, we needed to trim a little $$ from our budget and so worked with Homeco Insulators to come up with a sensible alternative without compromising quality or performance. Because our roof trusses are 14" deep, and have no light fixtures in our insulated ceilings, we had plenty of space to fill. We used 2" of spray foam against the roof deck and then did a "net and blow" installation of 12" of dense fiberglass fill (virgin wool - Insulsafe SP) with a poly sheet vapor barrier.There is also varying thicknesses of rigid insulation on top of the roof deck (and below the fully adhered roof membrane) to help direct water flow to the roof drains. The combination of these systems produces an R value of R50+ in the roof at less cost. At soffit areas and overhangs, we sprayed 10" of spray foam for and R60 rating. Working with our insulators from start to finish was great - they offered the best solutions for the challenges of this house and did a top-notch job. The 3rd party energy modeler and testing agent for the Greenstar and Energy Star program gave the installation an "A".
A look at the "net and blow" fiberglass installation below the roof decks. Note how all seams and penetrations (electrical boxes and bathroom fans) are taped and sealed. The fiberglass will be pushed up against the spray foam above by the gypboard at the ceilings.
In the attic space below the existing gable roof, we added vents, air chutes and enough of the same fiberglass insulation used elsewhere to achieve R50+.
On our foundation walls and under the new slabs, we used several inches of rigid, high r value XPS insulation to keep heat from migrating to the earth through our floors. This helps keep our feet warmer in the winter.
Convection is the transfer of heat in liquids and gases by the movement of those molecules from one place to another. As air is warmed, it expands, becomes more buoyant, and rises—a process called natural convection. Forced convection is the distribution of warm air by use of a fan or air handler.
Finally, radiation is the transfer of heat from one body to another via the propagation of electromagnetic waves. Heat moves from warmth to cold. When you sit in front of a fireplace and look into the fire, your face is warmed by the radiant transfer of energy from that heat source to your face. That radiant energy is not affected by air currents - you can still get sunburned on the beach even when there is a breeze. Most insulation materials function by slowing the conductive flow of heat. Materials with low thermal conductivity more effectively block heat flow than materials with high thermal conductivity. The R-value of an insulation material measures its resistance to heat flow.