I had not heard of coal as a storage medium. Maybe it's meant to be cleaner than stones or gravel. Yes, it appears you could merely turn off the venting system. The greenhouse would get warmer.

This document seems to have been written by the seller's real estate agent trying to a house that has issues. My first advice is to hire your own home inspector. I would be skeptical of an inspector recommended by the seller's real estate agent. Find a recommended inspector and be prepared to spend money to do get a thorough inspection.

If this house was built in 1982 then why does it have aluminum wiring. Aluminum wiring was not allowed in homes built after 1977. I personally would not buy a house with house with aluminum wiring unless I was prepared to replace all wiring with copper. It is is not worth the risk and the problems.

The write up states the AC is not used. It is probably old and needs to be replaced.

I am skeptical about this passive heating. Ask how is the house heat during the night when the sun does down.

There are a lot of unknowns, like the equipment used, the detailing of coal bed, crawlspace/basement, the type of coal, the greenhouse construction, the location (but sounds like northern living without a/c), how fresh air is provided, how dehumidification is provided (no a/c), etc.

The amount of time the coal will radiate heat will vary on the temp delta of the house and coal, and remember the coal may retain heat longer, but it is going through what sounds like standard wood framed construction which may not radiate heat as long. The system is not truly passive as it relies on powered fans to move air, and is not sufficient to remain in use for your climate as they only used the coal for spring and fall (so the savings on gas or electric would be minimal anyway).

It sounds like a standard furnace/thermostat setup with a/c (not working). So I am guessing they have routed some return ductwork strictly to the greenhouse, and some supply ductwork to the coal bed where the original house ductwork and the coal specific ductwork can be closed with dampers based on use. Whether they knew how to size the coal ductwork for the cfm the furnace provides the whole house (which if not can reduce the lifespan of your equipment), or where makeup air is coming from or return from a sealed "underspace" is unknown.

The greenhouse, which I initially pictured as a glass "hothouse," instead has siding and a roof, and claims to be multi-functional, although you need the temp to be 80-90d for the coal to perform which makes it pretty unbearable for living. It apparently is not maximized for solar gain.

It really sounds like a DIY bastardized house, not a designed-from-the-get-go passive energy home. So I would suspect the entire house and many other systems, repairs, and the design is at the level of a tinkering DIYer, so lots of compromises, jerry-rigging, directions required on how to use lots of things, and guessed-at engineering. The aluminum (circuit) wiring confirms this.

If I want to get professional help on any of this, whom do I start with? Will a inspector have knowledge on all this? Or general contractor know about howbto remove the over engineered green houz? I am in Washington Seattle area

This house seems like it has a lot of major problems, and could be a huge money pit. I would definitely not buy any house with aluminum wiring in it, unless, I got a lot of money off the price to completely rewire the house totally. Also sounds like it needs a whole new heating and cooling unit, which could be very pricey too. It doesnt sound like anything that I would want.

3ontheentree you seem to have got most of the guessing right. 😱😱 How much knowledge you guys have