required amount of light is not coming inside the room I have a bedroom scene in which there are two doors and two windows. Even Using portals doesn't give me results what is in my mind. I need illuminated inside scene. When both of the windows are open and doors are closed light should come inside the room and illuminate the scene. but, It's not happening even using the portals. in fact portal is not affecting the scene pretty much. first one is without portals 
this one is with portals..

hdri I have used is having 27EV. and I have set strength of 20 and still light is not coming inside the room. Link for hdri. and I am attaching screenshot of my blender screen where you can see strength as well you can see that outside wall is totally white.
EDIT :: By mentioning that outside wall is totally white I want to say that If I increase the strength It is lighting up the room but it makes outside wall totally white. In last I am going to make an animation in which outside walls will be there so If walls are total white there will be no meaning of that. I am attaching a screenshot of original color of my walls too. This one is with the HDRI strength 1. This one is having HDRI strength 20 where outside wall is complete white.  here is the link for my blender file click here...
EDIT :: One more thing if I am increasing exposure then It makes outside walls white too. This is a base model of my bedroom. SO In reality with these window enough light is coming inside. SO i am trying to achieve the look I see everyday in my bedroom.
You can use whatever strength value for the environment that works for you, so if 20 is too dark, you can use 200, if 200 is too dark, you can use 2000, so if there is not enough of light, just add more light.
One thing to keep in mind is that if you have glass windows, whatever light comes through them, becomes refractive caustics, and they are terribly slow to calculate and not accurate at all in Cycles. You should consider using fake glass shader with transparent shader mixed with glossy for reflections by amount determined by Fresnel node. It might be a good idea to avoid calculating shadows from the glass at all, because they practically do not contribute to the realism of the render at all in vast majority of cases, so you can have the glass of all the windows as a separate object and disable it's visibility for all rays except camera rays:

What's important in lighting is not the numerical values, you use, but their proportions compared to each other. The light of the sun on a clear day might illuminate the ground with 120 000 lux while artificial lighting on a desk in an office is required to be(and often is) around 200 lux(at least where I am). So that's the difference between a light bulb and the sun in reality... Keep that in mind. In a dark painted room like yours the difference between the inside and the outside would be huge as well. No need to be afraid of that. If you have the values their relationships in the scene set up the way it is not convenient for you to adjust the strength of the environment and keep the ratios, you can also adjust exposure here:

... or here:

Both are OK, the first multiplies the values in the rendered result, the second multiplies the values of all the lights in the scene if I am not mistaken.
You should use portals to speed up the render - the noise clears up faster if you use portals, but they should not have any influence on the looks of the render.
Note that you definitely do not need any add-ons whatsoever to have nice light in your scene. They might make it more convenient for you to set things up, but are completely optional.
Here is an example of how I usually set it all up(.blend file (134.03MB)). I hope that might be useful to have a look. Feel free to use all assets in the file under CC0 license if you wish.