Normandy rules (pg. 7):

"Buildings are now able to be destroyed if under fire from an
eligible unit or subject to a normal area attack. A scenario states
in the terrain features whether it utilizes destructible buildings.

The process for attacking a building is as follows:

1. Determine if the attacking unit is eligible to attack the
building. The attacking unit DOES NOT COUNT the firepower of
regular infantry, elite infantry, officers, or machine gun crews.
However, squads can still trigger charges which affect the
building.

1a. Target a building hex without a squad. A unit may target
a building for destruction within range and in line of sight. If
there is no squad in the target building hex, THE ATTACKING PLAYER USES THE FIREPOWER AND RANGE USED WHEN ATTACKING VEHICLES."

I don't understand:

"... THE ATTACKING UNIT DOES NOT COUNT THE FIREPOWER OF REGULAR INFANTRY, ELITE..." (1.)

and

"... THE ATTACKING PLAYER USES THE FIREPOWER AND RANGE USED WHEN ATTACKING VEHICLES." (1a.)

Can I destruct the buildings using units firepower or only trigger charges?

I think what its trying to say is that normally only vehicles and area attacks can destroy buildings and you use their firepower against vehicles. For charges you probably use infantry fire against vehicles too. When it says you dont use firepower of infantry, elite, and so on it probably means not for a normal attack.

As the rules stand now it's bloody hard to destroy a building. You need 6 hits at the same time which is pretty close to pure luck in most attacks and impossible for artillery and bombings which are usually 4 or 5 dice, stupid. As for the OP question you can attack with anything but you use the vehicle firepower rating.

Thanks, soldiers!

They could then have written: "Only vehicles and mortars can destroy buildings" .

Cyscott1, I use house rules for artillery and bombing (adding the cost value of strategy card in attack dices), but I agree, is really dificult destruct a building.

Maybe two Tigers in combined firepower (13 + 7) .

It means that regular infanteri cannot destroy buildings. Basicly you need a panther, a tiger or an demolision expert to do so. Having a demolision expert place two charges and destroy a building is fun!

However, I have one question, is it worth the time and effort to destroy a building?

And when I'm on the topic, please somebody include a scenario with 'destroy bridge' option for demolision experts

Grand Stone said:

http://app.fantasyflightgames.com/cgi-bin/quests/quest.cgi?command=comment&game=toi&scenario=2009090200441348622&admin_id=0

Grand Stone said:

In some scenarios, such as Battle in the Bocage, buildings are in the way of vehicles, so knocking them down helps you to get to the victory objective.