I have a circa 1895 -1900, 2 1/2 story century+ home that Richie's first insulated the brick wall cavities about 16 years ago, followed by spray foam insulation for the basement walls and crawl space about 5 years ago.
(That's only after have first having a long conversation with Murray and Andrew at a home show booth, followed by Murray's onsite inspection and quoting a year or two later.)
Being an analytical type I tracked my natural gas energy consumption afterwards for a number of years, using the science technique of calculated degree day measurement for London. The result was about a 30% fuel saving from the cellulose application which has been compounding each year since, and will be continuing forever!
I don't recall the savings for the basement and crawl space applications in the past five years, but may revisit doing so at some time when the inclination strikes.
To the present. After a great deal of consideration given to preserving my original wood sash windows covered with aluminum storms my current energy project is reluctantly replacing the original wood windows with new, vinyl replacements, while still keeping and even improving much of the historical nature of the home.
Some people will find that is an oxymoronic approach, even sacrileges. Yet properly performing such window restoration work oneself requires a vastly significant investment of personal time and energy, or finding a contractor specialized in such work is nigh on impossible and of great cost.
I've tried both approaches so have been searching for a blended approach that is cost effective, energy efficient and historically sympathetic. Even that's time consuming and more expensive than a simple replacement approach as is quite common.
In proceeding with the window project I again consulted with Andrew of Ritchie's today about whether insulating the weight and sash cord cavities was beneficial. His response was positive and to do so during the new window insulation by spray foaming into them, starting at the bottom and working up, drilling access holes as might be necessary in moving to the top of the cavity. That's a project I can do myself, or the window installer would typically perform.
This short, most recent conversation with a solution illustrates the sound, professional insulation advice I've always received in every experience and touch point I've had with Ritchie's. They care about doing the best quality job on the project, using their knowledge and expertise on each unique property to plan and and fill each hidden area requiring insulation - everywhere.
Granted, their lead time to a smaller project can be many months out. There's a good reason for that, and it's the superlative quality they apply to each and every situation, from quoting to completion, and even a subsequent touch-up that might became necessary.
Ritchie's are outstanding, perhaps even the best, in performing building insulation tasks, whatever the type and structure. A pleasure to deal with in every aspect.
I have been recommending Ritchie's for years to anyone considering such work and I do so here, unreservedly.