Confused about when toute changes to tout

Question

Sa sœur est tout heureuse de sa nouvelle maison.His sister is very happy with her new house.La Tour Eiffel est tout illuminée.The Eiffel Tower is completely lit up.

As you can see, in such cases, tout becomes toute in front of feminine adjectives, but only when they start with a consonant or an aspirated h.

But in the above examples tout did not become toute...what am I missing....???

Accepted Answer

Hi Jane, 
This lesson has just been updated to include 'tout' adverb, meaning very, completely. 
If you read the section again you will see that with feminine adjectives 'tout' will sometimes agree or not. 
I'll give you some examples ( as the lesson was very long we had to restrict those but it is intended to be split up at some point)
Elle est tout éblouie ( vowel - no agreement)
Elle est tout heureuse ( H mute, no agreement )
Elle est toute contente ( consonant - agreement)
Elle est toute honteuse ( H aspirate - agreement)
I will admit that this is the kind of mistake even French people will make as the rules are extremely complex!

Answer

Sa sœurest tout heureuse. -- His sister is very happy.Tout, in this sentence, is used as an adverb, intensifying heureuse. In this case, tout remains immutable, as mentioned in the lesson: The adverb of intensity tout can be used in front of another adverb to mean very. In this case, tout changes according to whether the following word starts with a vowel (tout) or a consonant (toute).