I do something similar, although not exactly the same. I am retired so I try to keep funds for major maintenance expenses available.
I have a savings fund that I keep in a balanced mutual fund in my taxable brokerage account. Keeping it in the balanced mutual fund gives moderate growth potential, low volatility and enables me to keep the amount separate from other funds in the account.
My savings fund is designed to cover replacement costs for car, roof, driveway, HVAC and major appliances. I estimated replacement cost and typical live expectancy for each item and it came to a savings amount of $5k/yr. I also keep a couple of thousand in cash in a HISA. If something like a fridge broke during a major bear market I could pull money out of my emergency fund rather than sell the mutual fund.
I cover smaller home maintenance like painting, plumbing repairs, furnace inspections/repairs etc from my regular annual budget, since those items are usually small enough to cover from general cash flow.