Both of us work from home for different employers and can claim in-home office expenses.
We had our furnace replaced last year. I believe we can claim a portion of this, but I am unsure if this can be claimed under each of our returns, or if we have to chose just one of us to claim it under.
The replacement of your furnace is considered to be a "Capital Cost", and CRA does not allow employees to claim Capital Cost Allowance (CCA) or depreciation.
Employees Earning Commission Income: You can deduct the part of your costs that relates to your work space, such as the cost of electricity, heating, maintenance, property taxes, and home insurance. However, you cannot deduct mortgage interest or capital cost allowance.
This link will take you to the CRA guide for Employment Expenses: https://bit.ly/2Ve3BM1