Go with the engineered wood. You're making it sound like refinishing hardwood is something quick and easy -- it isn't. Engineered wood will last you a LONG time.

If you feel the quality of engineered is inferior, you probably aren't looking in the right places.

Stay away from big box stores and the huge multi-national manufacturers.

I looked at this company when I lived in LA and was able to visit one of their locations. Excellent product. Even my third generation wood floor guy was impressed when he saw the samples (he was touching up our site finished floors before selling).

https://northernwideplank.com/pages/locations

I ended up going with a slightly cheaper manufacturer for my new build in FL because it didn't make sense to spend on a premium product in my new location. I ended up going with DuChateau engineered floors (hard-wax oil finish) and we've been very happy with them. Performing well with 3 dogs, much better than my previous site finished floors did.

https://duchateau.com/floors/signature/elements/riverstone/

Engineered hardwood floors are miles better than solid. You can use 11 inch wide planks to show off the beauty and grain structure of the wood. For solid you get 3.5 inches. Hardwood can only be refinished down to above the tongue and groove. 6mm engineered will allow the same number of refinishes. 3. 4mm allows 2 3mm one. The wood species currently available is European Oak. Less yellow without the open grain of domestic oak.

Monarch Plank.

"Is it true that we MUST use engineered? Does anyone have experience using hardwood with radiant? Are my concerns about engineered legitimate?"

You can install either solid wood or engineered wood flooring over radiant heating systems. Engineered wood flooring will perform better because it is more dimensionally stable and won't expand and contract to the same extent as solid wood. Your concerns about engineered wood flooring are no different from any other product: there are superior and inferior versions of just about everything. The quality and performance of finishes on high-quality pre-finished engineered wood flooring will outperform what can be applied on site. As advised above, stay away from products available in the big-box stores.

Not just any engineered can go over radiant. It has to be certified for that. Solid is a heck no. The best flooring for radiant remains concrete or tile. They do not have insulating properties like wood does. If you choose a finidh surface with insulating properties, the boiler, pump, and loops have to be configured with that in mind. Because the heat will not transfer as well as it does with a transmissive surface like concrete.

A good quality engineered wood is what you need. And they need to specify in writing that they will warrant it over radiant heat. You will have a limitation to the loop temperatures, so you need to work out the math with the HVAC contractor. That had better not be his first rodeo with radiant either. You will also need to pay for a whole separate HVAC system for your AC needs in the summer. Wood floors, cabinets, furniture, etc, all REQUIRE home humidity control, so you may need multiple ERVs with dehumidifiers and humidifiers to keep the moisture between 35-55% in the home. That is one of the drawbacks of not having forced air. It makes humidity control more difficult.

Engineered is awesome. Your concerns are unfounded

Engineered floors are better quality not worse. But the real issue - which you touch on - is that the thickness of the wood veneer on top can be very thin with engineered floors. So you should search for a manufacturer with a thick veneer that certifies it can be refinished at least twice. Get the actual thickness of just the veneer layer. You will find that none of the products sold in big box stoors have a veneer that thick. You might have to direct order this from a specialty shop.

Flooring Comparison: LVP vs Laminate vs Hardwood You'll need a flat subfloor. DMX 1-Step cannot be used with radiant floor heating.

• "Solid hardwood flooring is not recommended in floor warming applications." -- Can I install alternate floor coverings over Schluter...
• Technical Bulletin: DITRA-HEAT with Alternate Floor Coverings (conclusion: engineered wood provides in the worst performance among all supported floor coverings)

Biggest issue with solid wood flooring over cement is that it has to be nailed down. Not recommended for heat tubing in cement. The engineered flooring snaps together and floats on the floor. A special pad designed for being in contact with the heated floors is used but not expensive.

Real wood, solid wood floors are beautiful and can be refinishing if needed and your not going to sand down to the tongue n groove. I've done both. The manufactured flooring we used in our new home was made by Bruce manufacturing. Solid wood on top surface. So similar to solid wood.

I'll say this as a guy that worked with wood for many years. And used both types. The looks and even feel of solid wood floors is better. I used Bona products for the topcoat, big dogs n kids and its still beautiful.

You may die of old age before your engineered wood floors need to be refinished.

If you feel the quality of engineered is inferior, you probably aren't looking in the right places.

Good answer.

I'll say again: Don't look at refinishing hardwood flooring as something anyone can DIY or something you can knock out in a weekend. Refinishing flooring is REAL WORK or REAL MONEY.

Or, you can go with a wood look tile and not worry about wear and tear, or the wood's R value and instability working against the heat. Porcelain cal also transition from inside to outside.

https://www.daltile.com/products/wood-look/saddle-brook